From PlantNet key: Leaves glandular below; peduncles with glandular hairs and fine prickles Rosa rubiginosa Leaves not glandular; peduncles glabrous, without prickles Rosa canina So if there are fruit present, it is easy to look for the prickles below the hip to see which it is - prickles = sweet briar, no prickles = dog rose
As well as the PlantNet key, canes of R. rubiginosa are thornier. the sepals seem to be retained longer on the fruit of R. rubiginosa, which often has some prickles on the hip. I have made Rosa sp. (A Wild Rose) from plants growing close together. I had to be a bit selective because R. canina seems to have mature fruit earlier. Note also the shape of the fruit. Once you have seen a few, the species are relatively easy to distinguish.