The focus key in CARNAGE on Roblox is F. Hold F to focus, and then you can interact with the interrogation prompt when it appears.

Quick use

  • Press and hold F to enter focus mode.
  • While focused, you can click the prompt next to a person to interrogate them.
  • They may refuse, so it is not always guaranteed.

Extra hint

The same guide also says the game uses M for the Xebepad menu, which can help if you are looking for other controls.

If you want, I can also list the main Carnage controls in one clean table.