Barch came back to the Panthers, along with a seventh-round pick in the 2015 draft, for centre Scott Timmins on Saturday. The Devils also got Florida's sixth-round pick in next year's draft.
Barch has played in 326 NHL games with Dallas, Florida and New Jersey.
Boyes and Gilbert had been with the Panthers on tryout deals. Boyes had 35 points last season for the New York Islanders, and Gilbert is a veteran of 447 NHL games with Minnesota and Edmonton.
The Panthers open the regular season in Dallas on Thursday.