Most teams I have seen doing this (and my own team) use actual drawer sliders to slide the minibot out on. Basically, mount a plate on one of these sliders and attach your minibot to this plate (in a way that it can climb itself off). Then you need to find a way to actuate the drawer sliders. As far as how to actuate this motion, there are various methods I can imagine.
sideways scissor lift
long pneumatic pistons
linear gear and motor
spring loaded, release a locking mechanism
Our team is using a block and tackle system with a 7in stroke cylinder, I don’t know how well this will work.
My team is using drawer slides and we use pneumatic piston with a pulley on the end of it, and a cable around that pulley that attaches to the frame at one end and the back of the drawer slide at the other. It’s really fast that way, fast enough in fact to crush the minibot when it hits the pole if we don’t put control valves on the cylinder. Then, since we can’t pull the minibot back in with the cable around a pulley we just have springs that pull it in.