I've never known snails or slugs attack Rosemary or Oregano. But I imagine I have different gastropod species to you.

I have a plethora of slugs and snails and the only herbs they have ever bothered are parsley and basil. Rosemary, lavender, chives, thyme, sage and oregano all seem to be resistant to their predation. Or at least not high on their preferred menu list.

Deer also seem to follow the same pattern.

The woody herbs- rosemary, oregano, sage, thyme, , stuff that trends to last overwinter, those with a harder stem and tougher foliage seem to fare better with snails than softer stuff like basil. But your population might have evolved to eat what's locally abundant, so you might need to look into ways to discourage. Some of those include removing mulch and leaf detritus since that acts as shelter/nursery to gastros, and not watering in the evening or as frequently because they also love wet soil and areas.