Ray tracing in C++

I have made a C++ actor which gets spawned when the game starts. The problem is that the actor (a mushroom) does not fall to the ground. To fix this I set SetSimulatePhysics to true which didn’t work as the mushrooms ended up rotating (roll rotation), so I increased the mass which still had not effect and ended up rotating anyway. I have decided to perform a ray trace which I can use to align it to the ground but I am unsure as to how this works. Any help would be greatly appreciated.