The situation is currently a bit messy, with conflicting statements but it appears that Roblox should work again on Linux / Steam Deck with Wine eventually.
As a little refresher: Roblox acquired Byfron, makers of anti-cheat software. They've now fully integrated it into Roblox with what they now call Hyperion in their new 64 bit client. They made a choice to block Roblox in Wine with this update, giving an assortment of reasons but saying Wine was still a priority and then later seemingly backtracking on that a bit.
Hope is not lost though Roblox fans, as they've now put out a fresh comment on the subject to make it clear that while they won't support it officially, they aim to get it working again.
Here's the latest word on it:
To clarify one detail: while we have no plans to release a Linux client, we are aiming to support Wine again. It seems possible, and we see a lot of value in it as a way of letting people run on Linux without the large investment on our end of releasing a native client. For all the reasons described above, Wine won’t ever be something that we guarantee will work, but also for all the reasons described above, we’d really like to make it work.
Right now though, it's all just words of course. We'll have to wait and see if it happens.