I can't change my Roblox from Thumbstick to Keyboard

I am sorry I am unable to provide you with any further troubleshooting tips. Instead you can try contact Microsoft Support for further assistance: https://support.microsoft.com.

i'm not in tablet mode and pen and ink isn't activated

Try to update/install the drivers in compatibility mode.

Uninstall and update keyboard driver:
1. Press Windows key + X key when you are at desktop.
2. Select Device Manager.
3. Expand Keyboard.
4. Right on the Keyboard driver and click on Uninstall.

Steps to Update the keyboard driver.
1. Press Windows key + X key when you are at desktop.
2. Select Device Manager.
3. Expand Keyboard.
4. Right on the Keyboard driver and click on Update driver software.

Also, try to search for the drivers from Manufacturer's website and install them in the compatibility mode.

Uninstall and update mouse driver:
1. Press Windows key + X key when you are at desktop.
2. Select Device Manager.
3. Expand mouse.
4. Right on the mouse driver and click on Uninstall.

Steps to Update the mouse driver.
1. Press Windows key + X key when you are at desktop.
2. Select Device Manager.
3. Expand mouse.
4. Right on the mouse driver and click on Update driver software.

Mouse+Keyboard don't appear

drivers are already up-to-date