I think Roberson is a great defender, but I honestly feel that he gets a little to much credit on these boards. Is he one of the best in the NBA, sure. Is he all-NBA defense worthy, absolutely. Is he hands down All-NBA 1st Team Defense worthy...... ....I didn't think so last year, and a lot of the season left this year to go. Maybe, but I wouldn't say 100% yes. So my personal answer to the OP is no. Is he in the conversation, sure, but Kawhi, Klay, John Wall, Beverly are all up there too (imo above Dre, although I concede Beverly's size could give Dre the advantage). As TD mentions, LBJ and Draymond should be discussed. I don't watch the Bucks, but Giannis I hear is up there. I sleep on him, and I fully admit that maybe I'm biased since in a thread last year, I was corrected by a lot of people on Rubio. I don't think he's that amazing on D, but many others do. George and Butler are good on D as well. I think Gary Harris is developing into a great defender as well - maybe not in this conversation yet, but getting there.
And honestly, while they're bigs, some of them are still scary on the perimeter D. The Brow can defend anyone imo, and Gordon is impressive in what little I watch and read of him.