Yes, REDROOT is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, D 2, R 1, O 1, O 1, T 1.

Is it a valid word?

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

perennial woodland native of North America having a red root and red sap and bearing a solitary lobed leaf and white flower in early spring and having acrid emetic properties; rootstock used as a stimulant and expectorant

Also: sanguinaria canadensis.

Not playable in Scrabble US: TETTERWORT.