The present disclosure is directed to a rotor blade assembly for a wind turbine having a first rotor blade segment with a first spar cap segment and a second rotor blade segment with a second spar cap segment. The first and second spar cap segments are arranged together at an interface and are constructed of a composite material. Further, the rotor blade assembly includes a joint assembly at the interface of the first and second spar cap segments. The joint assembly is constructed of a first metal joint secured to the first spar cap segment and a second metal joint secured to second spar cap segment. Moreover, the first and second metal joints are welded together at a weld area.