The 13th international Conference on Southern Hemisphere Meteorology and Oceanography is happening in Christchurch NZ February next year. Currently plans includes both online and in-person sessions.
Sessions can be found here, there's quite a few sessions that ROMS based numerical modelling would fall under.
Of cause, I'd particularly like to draw attention to the session "Physical and Biological Connectivity in Southern Hemisphere Oceans and Seas" which I'm chairing.
Abstract submission closes on the 19th of September.