You can’t really “turn on CPU” in Roblox, because Roblox already uses your CPU by default for parts of the game and system work. If you mean make Roblox use less CPU or use the GPU more , the usual fix is to lower Roblox graphics and set the app to high-performance graphics in Windows.

What to do

  1. Open a Roblox game.
  2. Press Esc and go to Settings.
  3. Set Graphics Mode to Automatic or lower Graphics Quality manually.
  4. In Windows, open Graphics settings and add Roblox, then choose High performance.
  5. If you use an NVIDIA or AMD GPU, also check its control panel and set Roblox to use the dedicated GPU.

Why this helps

Roblox’s built-in settings can reduce load, and Windows graphics preferences can push the game toward the GPU instead of the CPU, which may improve performance or reduce lag. Roblox also has official performance guidance for reducing common bottlenecks and improving overall smoothness.

One note

If you meant “turn on CPU” as in fixing Roblox not detecting your processor, there is no separate CPU toggle. The better path is updating Windows, lowering in-game graphics, and setting Roblox to high performance in your graphics settings.