Indeed, Canary Islands are too far to be served on W patterns as would only be able to be served by a single crew with no changes (a UK/Ireland to Canaries return is about getting to limits as it is).
The only other ways this possibly could work is night stopping aircraft/crew. ie a STN based crew could do STN-NOC-TFS (overnight in TFS) then do TFS-NOC-STN.
Alternatively, a DUB crew could operate DUB-TFS-NOC (then transfer back to DUB) whilst a second crew from DUB would travel to NOC and operate NOC-TFS-DUB.
EasyJet do the former a fair bit with LGW crew and the likes of Jet2/TUI will do the latter in some cases. But for Ryanair, both cases would be unlikely I'd have thought.