No, you can't play Roblox on Nintendo Switch. There's no official Roblox app in the Nintendo eShop. Never has been.
I've checked multiple times over the years. Still nothing.
And before you ask - yeah, I've tried the browser trick too. The Switch browser sucks for games. It barely loads basic sites.
Why isn't Roblox on Switch? Nobody really knows. Roblox runs on everything else. My crappy phone from 2019 runs it fine.
The Switch can handle Minecraft. Fortnite. But not Roblox? Makes no sense.
Some say it's about money. Others think it's technical stuff. I think they just don't care enough.
Your options if you own a Switch: get a cheap tablet or use your phone. Seriously. A $100 Android tablet runs Roblox better than trying weird workarounds.
If you're worried about performance, check if shaders on Roblox affect FPS - spoiler: they do, but you can turn them off.
Probably Roblox will never come to Switch. They've had years to do it. If they wanted Switch players, we'd have it by now.
But hey, stranger things have happened. Just don't hold your breath.