High humidity is the key in converting submersed plants into emersed form. Rotalas need pretty high humidity normally but I'd try to start them out at or around 100% humidity for a couple weeks and then slowly reduce it. I think they'll be happiest if it's kept above 60-70% though. They naturally grow in rice paddies and other boggy areas so keeping the soil nice and wet will help too. I had a couple species a while back and they grew just fine alongside my emersed Crypts (>90% humidity, nearly flooded, moderate lighting).