Because of a lack of Midwestern records for brumata, an abundance of bruceata there, the fact this larva has no clear adult association, and the fact that the caterpillars are apparently difficult to distinguish, it seems better to place it to genus (despite the fact that it seems far more likely to be bruceata than brumata).

That seems right to me. Also, I don't think this caterpillar fed on rose, which was perhaps under aspens, so was likely done feeding and off its probable host. It was prepupal a day after capture.