Here is the full list of all 29 Red Orchestra 2: Heroes of Stalingrad - there are Single Player achievements.
Complete the German Campaign on any difficulty
Complete the Soviet Campaign on any difficulty
Complete all of the training missions
Complete the basic training mission
Complete the Commander training mission
Complete the Squad Leader training mission
Complete the Support training mission
Complete the Tank training mission
Beat German Campaign Chapter 1
Beat German Campaign Chapter 2
Beat German Campaign Chapter 3
Beat German Campaign Chapter 4
Beat German Campaign Chapter 5
Beat German Campaign Chapter 6
Beat German Campaign Chapter 7
Beat German Campaign Chapter 8
Beat Soviet Campaign Chapter 1
Beat Soviet Campaign Chapter 2
Beat Soviet Campaign Chapter 3
Beat Soviet Campaign Chapter 5
Beat Soviet Campaign Chapter 6
Beat Soviet Campaign Chapter 7
Beat Soviet Campaign Chapter 8
Complete the full campaign on recruit or above
Complete the full campaign on soldier or above
Complete the full campaign on veteran or above
Complete the full campaign on hero
Complete two different defense missions while successfully completing the map without loosing the first objective
Beat Soviet Campaign Chapter 4