Short answer: Yes.
Technically correct answer...
The RM32 with a Dante card installed can send and receive Dante audio with any other Dante device on the network, including an X32 that has Dante support. Once the audio hits the network, it's manufacturer agnostic.
What you're asking though is about the RM functioning as a "stagebox" and usually a stagebox is just an I/O box that the FOH mixer gets input from and sends output to and has some control over, like preamp levels, polarity, phantom power, etc. In that sense, no, the RM can't function as a true stagebox for the X32 since the X32 can't control the RM's preamps/polarity/48v/etc. It's also the case that the RM can receive audio back from the X32, but the RM only has digital inputs to its Channels and to its Dig Return 2track. It does not have a way for the X32's main mix to go directly to the RM's physical Main L/R outputs. In order to get the X32 main mix to the RM's Main L/R out, it would have to go to a pair of channels or the Dig Return, and that would have to be turned up in the Main mix on the RM.
So, yes, you can send the RM's inputs to the X32, but the RM will be functioning more as a separate and independent mixer (i.e. a monitor mixer for instance) that has a digital split to the FOH mixer. You'll still need to have the RM connected to a network or computer so that you can use UC Surface or a CS18 to control the RM, either just the channel Preamp/48v controls at a minimum, or as a full on monitor mixer.
