I am not sure there's still a Ro/Ro between Dumaguete and CDO. From Dumaguete to Dapitan are several Ro/Ro. For the most up to date schedules better contact the ticket booths @the pier.
Dapitan? https://www.fastcat.com.ph/schedules/#1521184634548-9bb50558-6399 Never been there myself. I assume you get to Dapitan and then take a bus to wherever you need to go from there.
I assume you specified Ro-Ro because you want to take a vehicle, but for anyone reading this who is interested to get to CdO from Dumaguete without a vehicle, there is one flight per day. Other flights go via Manila and Cebu City. As pointed out here already, it seems the ferry Duma > CdO has ceased and the port on Mindanao near Dipolog is called Dapitan. To give detailed information about buses is unnecessary IF you are going by car but I think buses are abundant from Dipolog to places such as Zamboanga City, Pagadian City, Ozamiz City, CdO.
From the pier, Pulauan, halfway between Dapitan and Dipolog it's about 2 km to the highway. To get there tricycles or habal2x are waiting, if your final destination is not Dapitan or Dipolog. If so, just take a (shared or paquiao) tricycle to one of these two cities.
Cebu Pacific flies Duma to Cdo at 4.30 pm daily (as far as my limited search shows) but I cannot find any direct flights to Tacloban. I believe the only direct flights available from Dumaguete are to Manila, Cebu, Davao and CdO.
