Yes, ROMANTICISM is a Scrabble word!

Letter values in Scrabble US: R 1, O 1, M 3, A 1, N 1, T 1, I 1, C 3, I 1, S 1, M 3.

Is it a valid word?

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

impractical romantic ideals and attitudes
a movement in literature and art during the late 18th and early 19th centuries that celebrated nature rather than civilization
an exciting and mysterious quality (as of a heroic time or adventure)

Also: romantic movement.