Roll20 have several Looking For Group (LFG) options to find people to play with.

1. The Looking For Group Tool tool built into Roll20. Games that starts soon called Pick-up Games can be found here.

2. The Looking For Group Subforum^(Forum) - The FLG section of the official Roll20 Forum

3. Try finding games outside Roll20's official channels. The r/Roll20 subreddit have a short LFG Guide with some community options.

4. Use the Player Directory to find other players who want to play same games as you.