The rain that bookends the film was not planned and completely on accident! On the days filming the exteriors, rain was pouring in between shots and making it difficult to shoot. The end result is an oddly poetic element that adds a lot to the setting, character and story of Roses.
Because of the unplanned rain, three shots in the film had to have VFX weather effects added in. They're all at the end of the film, including the last shot.
While troubleshooting how to film outside with uncontrollable daylight and unpredictable Vancouver weather, the filmmakers came up with the idea to shoot the film in black and white and color correct the roses red. In the end the decision paid off.