Physical Danger
You'll probably be moving some really heavy equipment. Don't drop it on your foot or throw your back out. It'll hurt. You're a roadie, not Superman.
To go along with that, make sure you keep up with good sleeping habits. If you're in a zombie-like daze because you've only gotten five total hours of sleep in the past two nights, the odds go way up that you'll mishandle that heavy and dangerous equipment.
Other than that, you should be alright. Of course, when you're on the road with rock stars there'll be more opportunities to participate in the debauchery and to maintain an abysmally unhealthy diet. There are some obvious physical dangers that could result from that, but we're not your parents; be responsible, you'll be alright.