My first piece of advice is to let you know that if you are ultimately drawn to roller derby because of the fun outfits and quirky names, then you are probably not looking at the right sport for you. Most "fresh-meat" (newbies) skaters start out with that mentality, and are weeded out very quickly. This sport is going to take a whole lot of dedication and time and effort. It's not just about looking cool anymore, there is some serious competition out there!

I didn't know how to skate on quads at ALL when I first started (nearly 3 years ago now!), and I picked it up more quickly than most others. I was at full scrimmage readiness in roughly 3-4 months, whereas most newbies take 4-6 months to become scrimmage eligible (meaning ready for full contact). If there is a roller rink near you, I'd look into getting out there as much as possible. Also, more and more leagues are offering fresh-meat training and/or bootcamps, to prepare you for what's next and see how you will progress before actualy committing to becoming a part of a league.

The other thing to consider is the cost. There are monthly dues. Uniforms. Travel. Skates are not cheap! Knee pads, mouth guard, helmet, wrist guards and elbow pads. All of these things needs to be replaced regularly! See if you can attend a few practices before you commit for sure to see if it's something you REALLY want to do. Do not take roller derby lightly, while it will be probably the best decision you ever make for yourself, the derby monster can be all-consuming!

Size isn't really a factor, in my opinion. Sure, you look at folks like Bonnie Thunders and Claire D-Way and think "I am way too big" but it is so not true.
I weigh in right now at about 185 (started MFP at 215). I have been skating for about 5 years now (Freshie class of 2008 for NHRD) and at my heaviest (220) I was still on the All Star team. Now, you may say "220 isn't huge" it is if you're only 6'6".


So, here is my advice.
As slickbritt already said, train when and where you can. Get your skates and just skate. For one, casual skating is a great calorie burn, and another you're training at the same time!

Quats and wall squats to build your back and thighs up, and crunches/sit-ups to build your core. Your core is key because you need to be low and solid.

Jumping rope is good too. Or hopping. Anything that makes you REALLY pick your feet up off the ground.

Find your local league, see if they have Fresh Meat boot camps or training sessions. Introduce yourself and start learning the basics.

Remember, and this is hard... never, ever, compare yourself to anyone on the track. They say all sports are 60% mental, and 40% physical. So, maybe Skater Jane is better at transitions than you, but no one can knock you down. Always congratulate yourself and do it often. If you're dedicated to playing and getting on a roster, you will get there.
If you don't make the "cut" the first time around, ask about reffing. You can learn the skating skills, and the rules, and then the following year get right back on the track for the playing part.

And lastly: Stay in love with Derby. When you start to say "Ugh, practice" take a week off, hit the gym instead, but remember... relationships go through growing pains, and so will your relationship with The Derbs.

That's all I have for now.
So, hit that track and start learning girl. There is a whole world of Derby out there just waiting for you.

I started Fresh Meat last fall, I had to pull out right at testing time because there was just too much life stuff going on that I decided I'd rather pull out before making a commitment to a team - but they're right, it's definitely a sport. I'm going back at the end of the month and I can't wait. I crave the contact. We did this one exercise - the gauntlet, and it was amazing. You're jumping and hopping, and skating, and throwing hits and taking them... It was one of the most rewarding experiences of my life - the external focus. Even if you're a little heavier (and I was, and am) derby provides you with a focus - you're not just skating around in circles, you're working all of your muscles but you don't notice until you leave and someone tells you not to slam the car door. Why? Because you have fun! I'm never going to have fun on a treadmill, but with my skates, there's a story every time.