I don’t think you can connect RT and ON1 in a particularly seamless way. You can invoke ON1 as an external editor in RT. If you do this RT converts the file to TIFF and then passes this to ON1. ON1 can work on this TIFF file and save it (as TIFF or DNG). However, it doesn’t automatically pass control back to RT. You then have 2 files available in RT - the original raw and the denoised TIFF. I think there is better integration with Lightroom or Capture1 through plugins. The ON1 documentation doesn’t specifically mention RT, but does say that if using Lightroom without the plugin and instead use ‘Edit In’ the process appears similar to that described above with RT.
The ON1 documentation also describes an automated way of passing images between Photoshop and NoNoise, but also recommends that for optimum results you invoke NoNoise in standalone mode and work on the Raw file, saving as DNG, before opening this file in Photoshop.
In general, ON1 recommend you denoise Raw files rather than TIFF ones for best results.