Andrew,
If you want to go ROTC or the Academy, you'll have to separate from the AF. If you get your bachelor's while on Active Duty, then you have the option of applying to OTS/Guard/Reserves or separating then doing ROTC while completing a master's degree. Both have their pros and cons, but you can search the site for that. You'll learn a lot more that way than us just spoon feeding you information.
edit: I stand corrected. Thanks flyingbull.