Well, Brodin is a LHD. He can play RD, but is best at LD. If Dahlin/Power can play RD, then Brodin would be the perfect partner for them. Still don't think it's wise for the Sabres to trade Peterka for him. Brodin is great, and would be perfect for BUF, handedness aside, but Peterka is 9 years younger.
Foligno would also be a good add for Buffalo, but you he is 12 years older, and more of a role player. I also don't think that he would be crazy about moving back to the dysfunction in Buffalo after establishing himself in MN.
Both teams are looking to have significantly better years next year, albeit for different reasons. Neither is particularly interested in trading for futures. Peterka for Rossi is equal value wise, but doesn't make sense for MN because they need, and don't have, enough Centers. Buffalo, OTOH, have Norris, Thompson, and McLeod as good young'ish C's. Rossi is not a need, unless BUF decides to move TT to the wing.
Spurgeon would be a terrific short term add for Buffalo, but the Sabres would be crazy to trade Peterka for a 35 yo, and I don't think that Spurgeon would waive to go to Buffalo(I'm assuming that it would be on his 10 team NTC list). Young, top 4, two way RHD's with size are near impossible to find in trade, especially for a moderately sized winger.