According to Wikipedia:
If so, Have it come to fruition.Spielberg discussed a sequel in 1989 with J. J. Abrams as writer and Zemeckis as producer. Abrams's outline was eventually abandoned. Nat Mauldin was hired to write a prequel titled Roger Rabbit: The Toon Platoon, set in 1941 to 1943. Similar to the previous film, Toon Platoon featured many cameo appearances by characters from The Golden Age of American Animation. It began with Roger Rabbit's early years, living on a farm in the midwestern United States. With human Ritchie Davenport, Roger travels west to seek his mother, in the process meeting Jessica Krupnick (his future wife), a struggling Hollywood actress. While Roger and Ritchie are enlisting in the Army, Jessica is kidnapped and forced to make pro-Nazi German broadcasts. Roger and Ritchie must save her by going into Nazi-occupied Europe accompanied by several other Toons in their Army platoon. After their triumph, Roger and Ritchie are given a Hollywood Boulevard parade, and Roger is finally reunited with his mother and father, Bugs Bunny.