This year, we grew roma tomatoes in two locations- pots and directly in the ground. Both started out as plants we bought from a nursery. I did not add any type of fertilizer to either of them. Both had full sun, although I believe that the pots actually got an hour or two more sun each day. So what were my results? The tomatoes I grew in the ground grew to the size I would expect. The ones I grew in a pot- well, they look a lot more like cherry tomatoes than romas, at least when it comes to size.
Next year we plan to grow all our tomato plants all in one area, all in the ground. But if I did do some in pots again I would definitely reach for some type of fertilizer.