Yes, BUCKAROO is a Scrabble word!

Letter values in Scrabble US: B 3, U 1, C 3, K 5, A 1, R 1, O 1, O 1.

Is it a valid word?

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

local names for a cowboy (`vaquero' is used especially in southwestern and central Texas and `buckaroo' is used especially in California)