A rotor blade for a wind turbine may generally include a first blade component formed from a first fiber-reinforced composite including a first thermoplastic resin material and a second blade component configured to be coupled to the first blade component at a joint interface. The second blade component may be formed from a second fiber-reinforced composite including a second thermoplastic resin material, wherein the second thermoplastic resin material differs from the first thermoplastic resin material. The rotor blade may also include an additional layer(s) of thermoplastic resin material positioned on or integrated into the second fiber-reinforced composite at the joint interface that differs from the second thermoplastic resin material. Moreover, the first thermoplastic resin material of the first fiber-reinforced composite may be welded to the additional layer(s) of the thermoplastic resin material to form a welded joint at the joint interface between the first and second blade components.