The short walk begins from a humble unsigned pullout just west of the small Rocky Creek Bridge. There's a small hydroelectric building and some signs giving the appearance that it's forbidden private property, but the trail continues to the right of the building and follows the brook all the way to the rocky base of the falls in about five minutes.

Even though it requires a little bit of rock scrambling at the base of the falls to get the best views, there are signs posted indicating that stream levels can dramatically increase without warning. The two takeaways I get from this sign are that:

1. You don't want to linger for too long in the stream (let alone swim at the plunge pool at its base)
2. This stream may have a hydro dam further upstream suggesting it's regulated (though this is just a hunch and needs to be verified)

This happened to be the lone waterfall we visited while in the Dosewallips State Park because the Dosewallips Road (unpaved with potholes a couple miles west of Rocky Brook Falls) leading to Dosewallips Falls further to the west was washed out. I have no idea if they're re-opening the road or if it's left in disrepair. Otherwise, there would've been another waterfall entry on this website from this area.