I've skied in La Rosiere and the Haut Tarentasie valley since 1999 and La Rosiere is my go-to resort, I visit every year, I have to confess a bias here but having skied in most Big resorts in Europe it's the friendliness of the resort that keeps me returning, as well as the opportunities for some serious skiing, it's there if you know where to look. The ESF offer a piste tour for visitors which is well worth taking. With a top altitude of 2800 metres with the lowest skiing at 1174 meters there aren't many resorts that can match that range.
The pistes in La Rosiere is all south or south-west facing with the exception of one north facing piste - which takes you to the link to La Thuile where all the pistes are north facing, so you have access to two different terrains on a single lift pass, which is extremely good value compared to other nearby resorts.
I've heard complaints that the drag between La Rosiere and LaThuile is too long and prone to closure when windy, the reason is simple the Col de Petit St Bernard is at 2200 metres and the wind in the mountains does blow from time to time. You just have to accept it because it's not going to change, but the attraction of skiing on the Italian side is worth it. For the experts the steepest piste in Italy is in La Thuile - pista 3, one of the steepest sites in the Alps. There is also a superb selection of mountain restaurants in Italy with great value delicious meals and drinks, this as also one of the reasons I'm a fan of La Rosiere, with a couple of notable exceptions food an beverages on the mountain are the same cost as in the village.
