There is no official Roblox on PS5 release, but that doesn't matter as you can use the PS4 version, so here are the details for how to set it up.

Roblox is cross platform on PS4 and PS5 as they both use the same version of the game, and broadly Roblox is crossplay compatible across all formats.

Roblox is coming to PlayStation 4 (PS4) and PlayStation 5 (PS5) consoles this October. The platform is also coming to the Meta Quest VR.