My two bits:
Today, I would buy a small underseat roller (WITHOUT SPINNER Wheels). The spinner wheels remove 1" of packing length from the bag, and you get more space in the old style wheels. These usually conform to Ryan-air size of specs for carry on (check before buying).
This would be the base for attaching another duffle type or non-roller bag. I also prefer non-rollers when i can. (I have a strap and hook that will attach anything, or my totes / duffles have a pocket sleeve on them to fit over the handle which is great). This small size, for me, would let me put my heaviest item (my laptop) in the roller portion, and attache or carry the lighter bag, instead of today where I carry my briefcase and have my light clothing in the roller bag.
To get stuff on board with the smaller EU allowances, soft bags are better -- hardshells don't squish that last 1/2 inch to prove that they fit the sizers before you board. So, you could look at a rolling duffle or a regular softshell (my preference).
I used to travel a lot for work. I am very impressed with how the American Tourister bag (max legal carry on size) I bought held up. I bought it in 2006, and it was my primary for years, then my husband's bag for the last 3 years. It is great and has been through at least 100 trips and I am not gentle with it, as it was not expensive (under $100). The handle over wrap came loose, so I suppose I could send it in for a free lifetime warranty for repair, but I just taped it.