Hi - are you hoping to take formatted text out of Salesforce and have it be formatted text in Workfront? Or just take plain text from SF and write it into a rich text field in WF?
I don't love WF's rich text fields because they don't display correctly in all settings, so we don't use many of them. However, I just jumped into Fusion and they appear to be working the same as any other field through the Workfront > Update a Record module.
We originally were pulling a Salesforce account description/notes field into WF, but we ran into character limits where we needed to build text truncation logic into WF. I think we did that work, but we stopped using it a while back, so I don't remember the details.