I believe BIG was already talking about starting his own imprint and signing artists. So it's not hard to believe he would've left after another couple albums.
Don't think BIG would sign with the Roc though. If anything, BIG might've made his imprint a whole new label and collaborated with Roc-a-fella like MMG collaborates with YMCMB. The only difference would be that a BIG Label-Roc collabo wouldn't make songs consisting of two lyrically mediocre stars who, at best, have been hit-and-miss in terms of quality their whole careers, and a bunch of other lames that can't ride the beat or rap anything above a 3rd grade reading level, or simp so much he looks Richard Simmons look like Michael Clarke-Duncan.
Also, BIG, from what i've read, was into that DC Go-go music. So I'd suspect, he'd have made more songs like what they were doing in the late-90's and early-2000's, and then once the middle of the last decade rolled around and the sounds started becoming more eclectic (into what they are today), we'd get a bunch of heavily gogo-infused music, with faster rapping.