The pair will both remain on the rookie list next season, with Gardner joining the club during the mid-season rookie draft and playing two games in his debut year.
Smith has played 17 career games, after making his debut in 2015.
“We saw some really promising signs from Roarke and Ryan in 2019,” Dogs’ General Manager of List and Recruiting, Sam Power told the club’s website.
“Roarke’s challenges with injury early in his career are well-known. This year, he was able to consistently play good football for Footscray and make an impact when given the opportunity at senior level.
“He’s good by foot and has the flexibility to play roles across all three lines.
“Ryan also offers great versatility, in being able to play as a key defender or key forward, and he provides plenty of competitiveness in the air.
“He was drafted on the back of some impressive form for Footscray, and while a knee injury restricted him later in the season, we are confident he has more to offer at AFL level.”