Is this a good bug or a bad bug? I have never seen it on my roses before and I would hate to kill it if it is a good bug.
May 23, 2021
Thank you for contacting the Toronto Master Gardeners. The bugs on your rose appear to be adult rose sawflies (Arge ochropus). They appear in the early spring and lay their eggs on the underside of host leaves. The larvae appear several weeks later and feed on soft leaf tissue for about a month. They then drop into the soil to pupate and then appear as adult sawflies. There can be two generations each year. It is the larvae that are the problem for your rose. If the level of infestation is minor, the damage to leaves can be cosmetic and rarely harm the plant. However if there is a heavy infestation, the plant can be severely defoliated which will stress and weaken it, leaving it susceptible to disease and other insects.
Check the underside of the leaves on your plant carefully for eggs which might not have hatched yet, and also check for larvae anywhere on the leaves. Remove infested leaves and destroy the eggs and larvae. You can also use a forceful spray from your garden hose to knock off and kill the larvae.
It is still fairly early in the season so your rose might not be badly infested yet. Continue to check it throughout the growing season.
There is information and pictures of this rose sawfly at this website :
https://inaturalist.ca/taxa/447507-Arge-ochropus
There is more information including how to treat rose sawfly at this website :
Good luck with your rose !