This article concerns the development of King's Quest IV: The Perils of Rosella.
There are essentially three different versions of KQ4. Besides the AGI version, there are two separate SCI versions, each with their own unique graphics, and in some cases, transcripts. The first SCI version (#1.000.111) had separate artwork for daytime and nighttime versions of each scene. The later SCI version (which is the one included with all KQ collections) simply pastes a night-sky backdrop on top of the daytime artwork. As a result, many of the game screens were significantly redrawn between the two versions; a few of the animations were altered as well.
Music and sound capabilities was the major enhancement to the game, over the previous games in the series.
The game did not have a Sierra specific composer, and instead had a Hollywood composer, William Goldstein. He was quite a character, and the first of any repute that Roberta had the chance to work with. He was a typical arrogant Hollywood type person. Roberta spent an entire week at his house with another sound guy from Sierra. They spent their time essentially babysitting Goldstein day after day, just trying to get him to work. Most of the time he spent messing around; either eating, messing around, talking with various servants, taking them out to lunch, flirting with Roberta, or other things. But every now and then, the time would be punctuated with brilliance, when they could actually get him to sit down and do the work. At those times it seemed that he'd punch out the songs, quickly. It as wonderful when he did it but it was exasperating week for Roberta.
KQ4 is known for having the first female protagonist in a computer game, or at least adventure games (Note: at least Samus Aran of Metroid fame was introduced to gaming two years before in 1986).
Roberta and Sierra considered this choice to be a female possibly controversial at the time in 1988. Up to then all the player characters were male (at the time the subscriber list for Computer Gaming World for example was 98% male), and most game players and buyers were male. The idea of creating a main character who was female was 'very scary'. Many people at Sierra were upset, and wondered what she was doing, they wondered why Roberta would make that decision, because no guys would want to play a "girl", and that Sierra would lose its customer base, and that she would destroy a great series. Roberta disagreed and thought it was the right thing to do.
Since the gaming industry was dominated almost exclusively by male players, Roberta chose to take a risk of releasing a game with a female character, fearing it would get criticized, but also hoping it would draw more women into gaming. This was apparently a success as the game was released to critical acclaim, and had more female players than previous games. It became the most successful game product of the year. However, at the time Roberta said that since many girls and women were already avid King's Quest players, replacing the hero with a heroine "felt natural, like it was time." 
- I knew the female lead is just fine for women and girls who play the game, but wasn't sure how it would go over with some of the men. And you know what? It wasn't as controversial as I expected. However, it was real strange at first designing the game; quite a different point of view. Having the women die bothered me more than I expected."
She had done three games, with male characters, and she wanted to introduce the series to women audience as well, expanding the demographics (to get them to play games as well). She believed it was the right thing to do and stuck to her guns. She thought it would be nice to bring a game to female audience, and make them feel comfortable with computer games, and increase the female base of computer game players.
At the same time she believed if the game was a good game, the character was good, and that it fit, that male audience wouldn't care what the player character was, as long as the game was fun.
Her decision did not affect the game sales, and it sold better than previous games in the series ("...better than the first three...").
According to a survey of the player's genders made after the games release; it was asked if they preferred to play a male or female characters. It was found out that by in large male player base didn't care if they played a male or female character, as long as the game was good, and it fit and felt good to them. The female audience on the other hand, preferred by in large, to play a female character. They didn't really like playing male characters.
Hidden in the KQ4 files, are extra animations for frog prince showing the back and front of his cape. In first version of KQ4SCI there are animations for a rather large beetle-like creature (a living scarab?). There is also a bouncy happy face animation. There are more animations and directions for Rosella used in the introduction closeups (that are not used in-game).
There is also extra animation for walking around with the frog prince.
In an issue of Sierra's InterAction magazine, a screenshot appeared of an early version of Cupid's pool. This image showed a fountain at the north end of the pool; it was later replaced with steps where Rosella can climb out if she falls in. The screen was almost entirely redrawn when the fountain was removed.
On the back of the KQ4 game box, a screenshot appears of Rosella outside the witches' cave. The three witches are visible as well, standing just within the cave mouth and facing her. In the final game the witches never leave the inside of their cave.
Also on the back of the box, an early screenshot appears of Cupid's pool by night. The image was later redrawn for the actual game, and much of the foliage that was originally cloaked in black shadow was made more visible and colorful. In fact, many of the night scenes were initially significantly darker, with much of the background vegetation visible only in an outline of black shadow. The final game made the trees and plants brighter and easier to see at nighttime.
Sierra's 1988 video catalog advertised KQ4, and showed off a work-in-progress version of the game that had several alternate backgrounds. Most notably, the introduction closeup of Rosella and Genesta, as well as the game's starting screen background, originally contained a prominent cliff which was later removed. As well, the narrator's text was at first captioned "Narrator," like the dialogue of other characters in the game.
KQ4's story and progression was originally going to take place over the course of five days. This would have likely lead to each of the three quests from Lolotte, Genesta's quest to get her talisman back, and the quest to get the fruit each represent a different day.