I haven't seen this posted, but here is the PFF grades for Robertson:
Overall: 65.3
Run: 80.8
Coverage: 84.3
Pass rush: 43.4
Snap count: 389
By comparison, Danny Trevathan:
Overall: 87.5
Run: 37.3
Coverage: 81.3
Pass rush: 51.3
Snap count: 849
Not bad company to be in.