Experts and BHG readers answer.
my roses are already showing signs of blackspots
The cold snap didn't cause your trouble; black spot is a fungal disease that thrives on tender young leaves. It is especially troublesome with wet spring weather. Treat your roses with a product like Ortho RosePride Rose & Shrub Disease Control. It is a spray that should be applied every 7-10 days until the foliage clears up.