Open Roblox Studio
Click Tools at the very top
Click Settings...
Click OK
Click Rendering
Click the arrow beside Bevels
Click Off
Click Close
Click OK
Exit out of every Roblox window open
Play Roblox
Enjoy the EPIC amount of lag reduced!
Results may very. I have tryed this and it worked successfully. Its compltely your choice to do this and im not taking any blame if something wrong happens or if you mess up.