I also tried this to integrate my Roundcube installation with SES - https://charmingwebdesign.com/setup-roundcube-use-amazon-ses-send-email/
However, this just breaks Roundcube when I try it.
I'm needing help with this too. Using Amazon SES. For the most part my e-mail is working now but I can't send anything out. It keeps getting bounced back. I've asked about it on the forum but no one has responded. Seeing how you posted this 11 and a half months ago, this doesn't give me hope that I will be helped here. Did you ever find a solution?