Both Perez and Rosales had been training with their new teams prior to the trade announcement on Tuesday.
Additionally, Perez, whose previous contract ended following the 2015 season, has agreed to a one-year deal with Vancouver. The 34-year-old Panamanian international signed with FC Dallas from Mexican club Tigres UANL in January 2012, recording 36 goals and 14 assists in 97 career regular season appearances with FCD. He had five goals and one assist in 23 regular season appearances last year, and tallied one goal and one assist in three appearances in the 2015 MLS Cup Playoffs.
The bruising, 6-foot-1 striker is the second leading scorer in Panama history with 39 international goals, and third all-time for Los Canaleros with 102 caps.
"We know Blas is an excellent player from playing against him in the past four years and we're excited to get the chance to work with him on a daily basis," Whitecaps head coach Carl Robinson said in a statement released by the club. "In the short period of time that he's been here, he's shown how he can help our team, and also our group of forwards improve. We're delighted to have him on board and the guys have welcomed him with open arms."
Rosales, 34, came to MLS in 2011, when he signed for the Seattle Sounders from Argentine giants River Plate. He spent three years with the Rave Green, moving to Chivas USA for a brief period in 2014 before being traded to Vancouver that August.
The creative midfielder has 13 goals and 48 assists in 142 career regular season MLS appearances. He scored one goal and registered three assists in 24 matches with the Whitecaps last season. The former Ajax player recorded 10 career caps with the Argentine national team.