Yup, it will be just like any other Pi3 RoonBridge endpoint in this case. You just need to turn up the volume on your powered speakers and then reduce the volume via Roon’s digital volume control, and maybe use Roon’s auto volume levelling for added convenience.
You just need to be careful when Roon’s volume goes to 100% (e.g. acccidental) but the Roon v1.4 update really improved things there with safety features.