I think Tobiah/Tobias and Rosette/Rosalie go together just fine.
I would choose
Tobias, so that you don't have all three boys ending in -iah.
And I would choose
Rosalie, because
Rosette feels a bit nickname-y next to the boys names.
Three boys nappin', one mama namenerdin'
To peruse my top 100ish names:
http://www.behindthename.com/pnl/82589
"My Inner Birthing Mother Paddles a Canoe" and other non-name musings
found on my blog:
http://jodifriesen.blogspot.ca/2014/07/paddle-power.html