In Estonia mosquitoes are always a part of a hot summer. But thankfully Roosta is near the sea and there should be much less mosquitoes there. Still prepare yourself for ants and flies. Also an insect repellent would be something we recommend to have. Most insect repellents prevent ticks, mosquitoes and other insects.
Since the nearest center where to get medicine is Haapsalu (39 km), then it is strongly recommended to bring your own medicine (painkillers etc).
Apothecaries in Haapsalu:
Südameapteek (Jaama 32, Haapsalu)
Apotheka (Tallinna maantee 1, Haapsalu, Haapsalu kaubamaja)
Benu apteek (Rannarootsi 1, Haapsalu, Rannarootsi Shopping Center)