Red Orchestra 2 (And Rising Storm) is not like other games (or game engines). The game creates a very CPU heavy load due to its feature set, and that makes the game CPU bound where most games are GPU bound. There are several settings you can change in the settings menu that will reduce CPU load. Try changing these to the lowest settings and see if it improves your experience:
In the video tab of the options menu change the following to lowest possible detail -
1) Shadows Quality
2) Detail Mode
2) Occlusion Quality
These settings should take some load off of your CPU and may improve your performance. For the best RO2/RS experience we strongly recommend a quad core 3 Ghz CPU or above.