Yes, ROSINWEEDS is a Scrabble word!

Letter values in Scrabble US: R 1, O 1, S 1, I 1, N 1, W 4, E 1, E 1, D 2, S 1.

Is it a valid word?

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

North American perennial having a resinous odor and yellow flowers
any of various western American plants of the genus Grindelia having resinous leaves and stems formerly used medicinally; often poisonous to livestock

Also: silphium laciniatum, gum plant.