I'm interested in learning if there is a version of lettuce or
"similar" vegetable that I can grow on my patio garden all year round
and not have to worry about the cold. I live in the Raleigh, NC
area. What handles the weather the best hear?

Kale or spinach are some of the most cold-tolerant.

In Raleigh I don't know if you could grow them all winter. I'm
guessing they'd either die off at some point, or at least stop growing
for a while. But late fall and early spring for sure.

You might be able to extend the season with some sort of
mini-greenhouse, for example this:
http://www.growerssupply.com/farm/su...;e055ab41.html
or this:
http://www.growerssupply.com/farm/su...;9620fe59.html
(something similar to the latter can be made from scavenged plastic
bottles or the like)