Yes, you can. Rovaniemi is a smal town. Even in the city it is possible to find dark spots with open sky view and enjoy the Northen Lights. For example, Kemijoki river embankment near the bridge. The Arctic Garden behind the Arktikum museum (10 min walking from Rovaniemi center). Or top of Ounasvaara fell (40-45 min by foot from city center). There is Sky Hotel observation tower.