[roofit] use reference in range loop to avoid copying of complex obj
[roofit] use reference in range loop to avoid copying of complex obj

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root