A woman friend bought a house a few years back, and the previous owner left some stuff in the garage.

What is this?
It's about the size of a baseball cap.

...?

I am guessing a wallpaper roller?

Need picture of the bottom of the black plastic side.

I hope this works.
I have a short video of her hold and turning it in her hand, but I can't figure out how to load a video to here that is NOT vimeo or youtube.
Here's another shot...trailer type of hitch device with a black rubber roller on the bottom?

...?

It's likely a device for those with lower arm strength to move heavier items that tend to be stored in the garage.
Sort of like those rollers at TSA checkpoints utilized to roll your carry on into the x-ray machine....but for heavier lawn equipment/tools/etc.

Thingamabob

its a dohickey

A whatchamacallit!?

It’s a clamp and roll.

A chingadera.

That's racist!

Disagree. Down here south of I-10, you would be surprised at how many chingaderas one encounters on a daily basis.

Kinda looks like a support off a miter saw stand. Maybe... Maybe not.