With relatively low base HP for a rare card of this type, Regirock is best used against those weak to Fighting attacks, such as Darkness, Lightning, and some Colorless pokemon cards
Choosing label types
Outside of a few casualty cards and Twinning Staff, I dont feel Parnesse is going to do a whole lot at the helm without a large deck overhaul
Professor Hojo has a Training Grounds-style discount for targeted activated abilities, as well as other benefits for building around those sorts of effects
But for the vast majority of creatures, indiscriminate damage will perform just fine
There are many other cards that are tagged on as forest art on sites like Scryfall if the art depicts trees or forests, like the Fallout Farkseek reprint, but those are outside of our scope today