Free Games:
- The Finals (very well polished FPS)
- Fortnite (fortnite :p)
- FNAF Pizzeria Simulator (on steam, forgot the title)
- Poppy Playtime Chapter 1
There's also free games on the Epic Games Launcher you can claim occasionally.
Good Demos:
- Deltarune Chapter 1 & 2 Demo (if not already played).
- Berry Berry Bury Demo (forgot the title).
- Every Steam Next Fest game, there's a couple of good demos there too.
- On Switch, there's a million Kairosoft tycoon game demos. I played a lot of those while I was bored.
For Roblox, I don't know.
Wait actually there's a couple of Roblox games I know, but I don't really like any of them anymore and haven't played roblox in a long while:
- Jailbreak
- Ink Game
- Prison Life
- Death Penalty
- Impostor, that one among us ripoff
(except for like these games):
Good Roblox Games:
- Deltarune Connected
- M.E.G something, high-effort backrooms game