You want Mouse Guard.
There is no licensed game for Red wall, but the Mouse Guard RPG is the closest thing you will have. Based on the David Petersen comic, in the world of Mouse Guard, "Mice fight to live safely and thrive amid harsh conditions and a host of predators," which he has in common with Redwall. David Petersen himself commented on Red wall with respect to Mouse protector in his blog post commemorating Brian Jacques:
Red wall was so much an influence on Mouse protector since it was an anti-influence. It was while developing ideas for my own group of mouse explorers that they handed me the first book in the series. I really enjoyed Brian's writing and his gift for including vocal accents in the text. I was further burdened by the desire to pursue my love of animal stories and medieval cultures.
However, I knew instantly that I could never get over what Mr. Jacques was doing. So when I say that his books were a counter influence, I just want to say that I had to take a different path than he was already a teacher.
The Mouse Guard role-playing game deals with fantasy rodents and small people culture, handles combat well, and is a beautiful game as well.