Making a test tiny roast
I make a lot of home cured corned beef so the seasonings are pretty set. When I first started, I didn't try to make a soft tiny roast to test the seasoning, instead I sliced off a thicker slice and cooked in slowly on the stovetop until it was done to my liking then tasted it. I wasn't worried about making it soft and tender when I was testing for seasoning.
One of the best ways to make a roast soft and tender is to use a sous-vide immersion circulator. Set it to your final temperature, let the water heat up,  put the roast in a plastic bag, remove the air and cook until tender. You can find dozens of resources about sous-vide cooking on-line.