Surely that is not the entire error? Would be helpful the see all of them.
For now I can spot that in your header the function argument roomList_ is a reference to TArray<Room> while it no longer is a reference type in the cpp file.
void ASomeActor::SomeFunction(TArray<Room>**&** roomList_) // or leave this unchanged and remove the & in the header file
{
//...
}
Another thing I can only speculate about is that Room is either an Actor class (a UObject) or a struct and should therefore be prefix with either A, U or F (depends on your “Room”).