I think Niwan Rolls King is very well named considering their rice rolls are indeed really flavourful and better than most dim sum restaurants. I can't compare them to the rice rolls in Sam's congee though since the type of rice roll they do are kind of different. But overall, great texture and flavour in the rice rolls and they are also very generous as well. I believe the avg roll is around 3.99 with specialty rolls being 5.99. Very decently priced in my opinion.
I also really recommend their congee. As my dad pointed out, they actually took the time to make the congee base from scratch and apparently you can distinguish this visually when you look at the rice in the congee and see that they look like they've "burst" from their original grain form. Both my parents who are definitely not congee noobs said that Niwan's congee is in fact better than Sam's Congee with better tasting ingredients to boot.
The only thing I would steer away from is the variety of fried dough sticks they offer. Other places, in my opinion, do it better so I would really just stick to rice rolls and congee at Niwan. Additionally service was also fast and friendly which is what I always appreciate at my asian restaurants! Great addition to the new/not-so-new plaza at midland and finch!