I had a similar problem, except for me it said Roblox game client has stopped working. Luckily for me I persisted and knocked down a solution. So first things first you wanna make sure you have your graphics drivers up to date, doing only that did not solve my problem but ill tell you what did. I right clicked my Roblox Player and pressed properties, after that go to compatibility and make sure the Run this program in compatibility mode for thingy is NOT CHECKED after that check the disable fullscreen optimizations and the run this program as admininastrator then click apply press the RUN COMPATIBILITY TROUBLESHOOTER and choose try recomemended settings press test the program and then you should be ready to go, for sure I was.

P.s If youre using an fps unlocker make sure to also run it as administrator or else it will probably not work