Rise is a way of creating an updraft, which can be useful as a boost to get aircraft to altitude quickly, including bombers. Unfortunately, it doesn't appear to effect the formation evenly so that the drones tend to get left behind and lost. A hint though, level off and gain some speed, then use Auto-Angle (SHFT-X) to set a nose angle near level, before engaging the rise. If not, you may find your aircraft stalls. If you have it on normal auto-pilot (X), then the aircraft will nose down trying to maintain level flight and can lead to overspeed/overstress crash.
I use rise all the time to get to higher altitudes in bombers so I can practice bombing. I don't worry about the formation... they don't add anything other than a little more damage, which is typically kind of pointless offline.
-Soda
AH Training Corps
The Assassins.