There's a little bump on their feet like in the palm area that is 4 times larger on one foot than the other. He is visibly limping and favoring it.
Does anyone know if this is something common?
Looks like you've got a case of bumblefoot! There are several options for treating it. Many people go the surgical route: http://www.backyardchickens.com/t/236649/bumblefoot-surgery-with-pics-and-how-to
Some people inject 1/2 cc of penicillin into the swollen area
I like to first try spraying the swollen area several times per day with Vetericyn wound and infection care and see if that works. If it doesn't surgery is probably the best way to go. An important note on surgery, make sure afterwards that the wound is kept VERY clean. Secondary infections can develop that are worse than the initial bumblefoot.
Hope your roo is back to normal soon! :)