There's definite contact but it's made with the sole of his foot, hard to believe that would have been enough to bring him down, but I'd need someone to do it to me while I'm sprinting to know for sure.
Also it's easy for Howard to say penalty from his armchair but it's another one to give it when all eyes in OT are on you, he would know that himself, often saw him decide to make no decision during his career.
Stupid of Rojo to slide there, but even worse from Fellaini to get beaten by man and ball so, so easily.