From @alvestrand, in private email:

Section 6.4 is weak on guidance on how ICE with RoQ should work - should
there be ICE packets outside of the RoQ connection, or inside it? If
inside, are we using the "demux" method (first 2 bits) of distinguishing
ICE from RTP?

There is no mechanism defined to specify RoQ as an ICE candidate in the
same way as a TCP or UDP candidate can be specified. This has
implication for the "proto" field - if you want to make it impossible to
pick and choose between UDP, TCP and RoQ connections, probably mention
this explicitly as "out of scope - ICE with RoQ is for further study".