I flew on an Air Canada Q400 just last week (YVR/PDX).

No option for gate check or gate valet service there, either. They were tagging extra bags and slightly oversized bags at the gate. If it wouldn’t fit on board, they were putting it in with checked bags, tagged to final destination.

My rollaboard is a standard/small-ish hardsided case. The gate agent told me I shouldn’t have a problem with it, and didn’t make me check it. (I had to stuff it in the bin, but it fit.)