Wear sweatpants with the elastic at the bottom of the leg.
Depending on how tall your socks are you could stuff your pant leg inside your sock? This is why I always wear shorts when playing. But playing live in the winter time makes it tough.
Check out any recent video of Neil Peart... he uses a bike pant clip / reflective ankle belt to hold his pant leg in place. Similar velcro elastic leggings, available in olive green, camo, and black, are sold to the military to blouse their trouser legs on top of their boots, two for about $1.25 US.