Near you there is a popular botanic garden (on march opened sunday 10.00-16.00), take a cuple of hours to visit it. In the other side of the town, over the center, there is the adige mounths, and there, between river and sea, a panoramic tower where you can pick fantastic photos.
Two other things: at 4 km from rosolina mare to the highway (E55), opposite the river, you find a road called ‘via delle valli‘ , a fantastic road sourronded by the lagoon and a fantastic nature…you can even doing birdwachting.
Lastly, over the botanic garden, in the lagoon, there is little wooden floating dock. Whell, if you llike sunsets, go there at the right time, sit down on the dock and watch e the best sunset you never seen.