Most care info I've seen on rosys recommends waiting until the female is at least four years old. The waiting is hard, I couldn't do it so I broke down and bought an second female, an adult, so that I could breed her to my male while my little girl was growing up. I bred them last spring and she had four big healthy babies.
You might want to check out cobra brand heat mats:
http://www.herpsupplies.com/subcategory.cfm?id=2&sub=25 I use them on all my snakes and they seem much less prone to overheating than other brands. The Zoomed brand heat mats I used had me concerned about fires too. If the heat mat is running hot, you can get a dimmer, rheostat or thermostat to regulate the power supply (to regulate the temperature) to the mat. Using a set up like this, you could bring your costs down considerably if that is a concern.
-Alice