Mulch which is in direct contact with the stem or trunk of a plant also provides a direct avenue for invaders to crawl up that stem or trunk without even having to work for it...
And direct-contact mulch can restrict the air circulation at the trunk, inviting diseases and/or insects to drop by.
I have wood-chip mulch around my roses, but I've left a 2", max. 3", radius clear at the bottom of each plant. My poor roses...they have enough difficulty without me extending an invite...but that story is chronicled elsewhere.
Sunset Zone 17, USDA Zone 9