There are 3 10-letter words that start with 'roo'.
| rootedness | rootstalks | rootstocks | 
Note: These 3 10-letter words that start with 'roo' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with root, room, roof, roos, rook, roor, rood.
4-letter words start with 'roo' (5)