Yes, ROUNDEL is a Scrabble word!

Letter values in Scrabble US: R 1, O 1, U 1, N 1, D 2, E 1, L 1.

Is it a valid word?

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

English form of rondeau having three triplets with a refrain after the first and third
round piece of armor plate that protects the armpit
(heraldry) a charge in the shape of a circle