A.T. Robertson Commentary Romans 15:12

"And again, Isaiah saith, There shall be the root of Jesse, And he that ariseth to rule over the Gentiles; On him shall the Gentiles hope." — Romans 15:12 (ASV)

The root (η ριζα). Rather here, as in Re 5:5; 23:16, the sprout from the root. From Isa 11:10.

On him shall the Gentiles hope (επ' αυτω εθνη ελπιουσιν). Attic future of ελπιζω for the usual ελπισουσιν.