It would be far better put in the ground, you could keep it in a largish pot and keep it root pruned, have seen this done but to be honest they are best in the ground and dont forget the rowen tree has alot of superstition attached to it, a lovely tree though with great autumn foliage and berries.

I have one in my garden and would say its the wrong choice for even a large pot.

Not a tree I would recommend for a pot however large - it will want to grow to several metres in height.