Yes, ROM is a Scrabble word!

Letter values in Scrabble US: R 1, O 1, M 3.

Is it a valid word?

ROM is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

(computer science) memory whose contents can be accessed and read but cannot be changed

Also: read-only memory, read-only storage, fixed storage.