Moving Videos on Green Screen (This is in blender cycles.)
So I have a tank animation with a green backdrop and on that green backdrop I put a road so it looks like the tank is moving on the road. But the video clip of the tank is stationary so is there a way to move the video clip across the road backdrop to make it look like the tank is moving across the road? Also is there a way to reposition the tank like rotate it to make it aligned with the road backdrop or rescale it? I wish I could send a pic to make it easier but stack exchange crashes when I do. 

(This is in the compositing node editor)
So my node set up is the army tank with green backdrop in a movie clip node connected to the image of the keying node which is connected to the 2nd image slot of an alpha over node which is connected to composite. The road image is in an image node connected to the 1st image slot of the alpha over.
How I would do it 

Your best bet for scaling, rotating, moving, and animating all that stuff would be through the VSE. 
1. In the compsitor remove the green background to make adding the background easier later on using the keying node. 
2. Open blenders VSE and add in your newly rendered transparent video through SHIFT+A > movie 
3.With your clip selected add a transform strip via SHIFT+A > Effect Strips.. > transform. Once there you can change the size rotation and location all from the properties panel on the timeline. Your probably going to want to keyframe the movement of the tank so using the timeline put the timeline where wish and using the transformation strip you can change how the tank looks relative to the frame. Hover over the location, roation, and whatnot and then press "i" to keyframe it. 
4. After you render that run through the compsitor with an alpha over node and add your pic - that should do it. 

References 

https://www.youtube.com/watch?v=h0F5X4b7jug 
http://blenderartists.org/forum/showthread.php?261401-how-i-add-or-active-keyframe-for-VSE-blender 
https://www.youtube.com/watch?v=0PZ_cxjxexM