"Tell him he's wrong. Tell him that he even if he's right about waiting, he's right for the wrong reasons, and that makes him all the way wrong."
How to begin with Bert...?
Cuthbert Allgood is a gunslinger from Roland's past, one of sai Deschain's oldest friends. We know that he has died, and we know that Roland is bothered by what happened. Possibly he died for Roland's quest to the Tower, we don't know now. Of course, he may not be dead now... but don't get me started on that one. ;)
Bert was with Roland through much of his life, and always felt that he could never be quite as good as Roland; that he would always be the eternally second. Roland seemed to reach milestones before Cuthbert, who was both angered and dismayed at this fact.
All the same, they got along. It was a gunslinger's life, after all... Because that is what they became; gunslingers. During the perilous fight in Wizard and Glass, Bert, along with Alain, proved themselves to be as worthy of being a gunslinger as Roland himself was.
Cuthbert had a seemingly endless sense of humor. He made light of almost everything, and talked until he was told to shut up. Through this, he could be dead serious, and quite thoughtful as well. How could you not like the guy? Wh-at? Oh, and he named his horse Glue Boy. Yeah Glue Boy! See? Sense of humor. :)