The answer to your question is going to largely reflect your idea of definition of a "nice" yard.
If you live in an HOA (Home Owners Assoc.) and they are going to give you trouble if you don't have smooth immaculate pool table like lawn, I think you're stuck using a roller.
My law is pretty lumpy, and I don't care and neither do the neighbors. As a general rule, nature hates smooth, groomed uniform monocultures. So, in a sense, you're pushing string uphill to try to keep it very smooth.
But if you need it or want it for whatever reason, it will need rolling, which will compact the soil, and then you could and should aerate.
Paul W. wrote a pretty thoughtful article on yard care which you may find liberating...
http://www.richsoil.com/lawn-care.jsp
Finest regards,
Any thoughts..