Role Synergy
Armor and a sword alone do not a knight make! Planning to joust? Obviously you'll want ranks with a lance... and some ranks of Athlete(Horseman). Your opponent is probably adding his skill at riding to his roll, and it might give him the win even if you're better with your lance.
The Role explanations below list a few synergy examples, but players and GMs should negotiate any that reasonably apply. If it makes sense, do it!