More specificity about how they’re getting to Turtle can help.
In general if they are just coming up from Reverse de la riva or something with a single Dante Leon style you can try being more proactive and pressuring forward/snagging an underhook to force them back down.
If you’re passing and they immediately bail out to turtle, look to getting a grip across their hip (or on their near-side hip ion their gi and anchor your elbow down) to prevent the rollaway.
And if you’re attacking the turtle either get to their side to look for chokes/hooks/seatbelt, or if you have to face them head-on look for a front headlock control before they can build up and attack you