You can play Arché with your Seaboard in Single-Channel Mode, but you will not be able to take full advantage of most of the Seaboard's special features.

Mapping the bow

As with any other MIDI controller, you first need to map a control element to Arché's virtual bow. This is what lets you move the bow and produce a sound from Arché in the first place.

Because the sound generation takes the speed and acceleration of the bow's movement into account, it is best to map the bow to a control element that offers some travel and that can be controlled independently from the fingers playing the pitch. Any of the three touch sliders on the left hand side of a Seaboard RISE work well for this.

Please note that Arché's "Natural" and "Hybrid" playing modes will retrigger the sound when you move the bow backwards, meaning when you decrease the value of the mapped control element. In "Expression" mode the sound does not retrigger in that case but is sustained instead, which also makes it possible to experiment with mapping the bow to something like the "Pressure" dimension of a Seaboard.
 

MPE

For polyphonic playing, please note that Arché is only mono/duophonic and does not currently support MPE. See this article for details:
https://expressivee.happyfox.com/kb/article/77-is-arch-supporting-mpe
 

Pitch bending and glissando

Glissandi are not part of Arché's physical modeling engine. The pitch bend range is limited to a maximum of plus or minus 2 semitones, which means the "Glide" technique of a ROLI Seaboard is not possible.