Any possible problems you'll encounter will more than likely be the result of conspecific aggression that has nothing to do with what actual species they are, but their body shape and colours. Severums are a picky bunch when it comes to keeping multiple in the same tank, at least in my experience.
Honestly I doubt you'll have any problems, but I suggest you be prepared in advance to get rid of runts or hugely dominant specimens as in my experience, if they dislike eachother for more than two weeks to the point of constant cowering and bullying, they'll dislike eachother permanently.
Gold Severums are generally 'softer' when it comes to aggression also, and I believe Rotkiels might be similiar, but we don't have them over here so I couldn't tell you first hand.