I have a two-foot brass track screwed down to a four-inch-wide length of pine. You can see it in the background of the first picture. Mostly I use it to make sure I get the couplers aligned to the right height when I’m changing out couplers (second picture). Everything else I test out on the layout. I’m strictly onboard power, and, since I’m regretfully a zero when it comes to locomotive motor electric workings, I don’t need a roller system…I give 'em to Kevin when they need that kind of work!
edit: strange…I changed the number of the freight shed picture, but the same picture published twice, so I copy and pasted the picture location and it worked fine. Oh well, at least it’s there now. My height gauge is steel construction shims stacked and glued to the correct height with the coupler glued on the top. A lot cheaper than those fancy ones Kadee makes.