User blog comment:B214/Volume 23 discussion blog/@comment-31.11.129.16-20170319160510/@comment-10330822-20170319173400

Roygun could join Issei's team if Issei wanted her, but he'd have to substitute someone to use her. Right now, Issei can have both Bova and Nakiri in his Pawn pool, since they take up 3 and 5 pieces respectively, but he will switch Bova to Rook if he wants to use the pieces for Elmenhilde, since she is 2 pieces.

Chances are if Roygun is being used, she would either have to be given the Rook spot or Nakiri and Elmenhilde would have to sit out, because I doubt she takes up any less than 4 Pawn pieces. Truth be told the best would be if she only takes up one Rook piece, so you can just have Bova and Nakiri as Pawns, because, let's be honest, Elmenhilde isn't as useful as we hoped.