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