I am wondering what technology should I use to transmit data (enough for controlling the robot and receiving video) over dozens of kilometers and mountains ?
How far is it in kilometers? What radio frequency you can use? Do you need security (code the data)?
It strongly depends on your application, it seems you need a real-time connection (to control a robot).
In practice you can use an infrastructure such as telephony systems, GPRS or if you have enough resources you can use satellite solutions.
Another solution is to make a network or repeater of ZigBee modules.
You can use high power(1W) radio modems such as digi XTend or RFD900 for controlling your robot. For video transmission you can use high power analog video modules. Using proper directional antennas such as patch antennas or helical antennas, you can easily go up to 20+ km in line of site.
You're posting somewhat of a contradiction. If you want a radio signal with enough bandwidth to transmit video, then you'll have to use line-of-sight communications.
To do what you're asking, you'd need more of a network solution, or a very high vantage point (i.e. somewhere in the atmosphere) for your control antenna.