Yes, ROSELLE is a Scrabble word!

Letter values in Scrabble US: R 1, O 1, S 1, E 1, L 1, L 1, E 1.

Is it a valid word?

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

East Indian sparsely prickly annual herb or perennial subshrub widely cultivated for its fleshy calyxes used in tarts and jelly and for its bast fiber

Also: red sorrel, jamaica sorrel, hibiscus sabdariffa.

Not playable in Scrabble US: ROZELLE.