Robert's as a young kid was originally a fullback coming through the grades. Like most young talents, they're too good to not be in first grade, but usually their preferred position is already occupied, so they get placed on the wing, and eventually make do playing wing or centre. It happened with a lot of great players. Hodges, Inglis, even Lockyer had to bide his time till he got his preferred position.
Robert's is good under the high ball. His handling issues at the Titans came from trying to do too much. He was rarely put into space, instead he had to create his own space. Since he was the only one who could pull off something special, often the Titans just gave him the ball and hoped for the best. At the Broncos, he won't need to do everything on his own, which will lower his errors significantly. With Milford, Hunt, Boyd out the back, his role is already much simplified.
I think If he wanted to make the transition to fullback down the track, he would be able to so successfully. Coming through the grades, he did remind me a bit of a young Inglis at Melbourne, and I can see a similar transition to fullback if he chooses too. He already has blistering pace, deceptively strong, good footwork, great overall awareness and instincts and a hidden passing ability (albeit it may still need some work). He has all the attributes to make a good fullback.