This seems like a Chrome OS problem, and definitely not a roblox one. Your computer might also be the cause of the problem. The Pixel Slate has integrated graphics, my theory is the cpu can’t handle the roblox graphics.
Questions:
Have you tried restarting your computer?
Have you tried reinstalling roblox?
What are the specs of your computer?
I doubt it has to do with a hardware limitation as the mobile app is designed to run on even less powerful hardware than the Slate’s. Also, the problem disappears when the Chrome OS interface is visible.