We spent a week in La Rosiere from 12th to 19th January. We stayed in Eucherts, which is fairly quiet, with a limited number of restaurants open in the evening. Our apartment, in Les Balcons de la Rosiere, was pretty much ski in/ski out. The weather was quite poor - mist and snow most days and very cold. There are few opportunities to ski outside the main bowl in La Rosiere below the tree line. The bottom part of Marmottes was usually out of the mist. However, the red run down to Ecudets was excellent and was usually covered in untracked powder first thing in the morning. The lift back up the mountain is, unfortunately, rather slow, taking the best part of 15 minutes. The black run down to the same lift was a fairly soft touch.
We did get across to La Thuile on several occasions and there is more skiing in the trees. The red run 6 down to the resort was good, and red 7 was better than some reviewers have indicated. Most of the other runs above the tree line are wide unchallenging reds and blues. There are three lifts on the Petit St Bernard Pass side of the resort. We only did the red runs next to these lifts and they were all good. It's best to do these in the afternoon as they were shaded and very very cold in the morning. This side on the mountain can be quite windy and one morning the Fourclaz Express closed just as we got to it. The only way back to any skiing from there was the long red run 7 right back to La Thule. On a more positive note, both the Fourclaz and the San Bernadino Express lifts are covered which helps to keep the wind chill at bay.
The two drag lifts from La Rosiere to La Thuile aren't really a problem. They are long, but not very steep and I suspect that you would get equally as cold if you were on a chair. It is possible to miss out the second drag by skiing a long traversing blue/red down to the Fourclaz lift. From here you can access the excellent red runs (17 -21) on the left (south) side of the La Thuile.
Returning to La Rosiere required a bit of effort. The two long blue runs from the top of the Belvedere chair have several flat spots on them and boarders might find themselves doing a bit of walking.
Overall, the two resorts will provide enough interest for intermediate skiers for about 3 days and beginners will enjoy the open area above La Thuile and the blue runs around Eucherts and La Rosiere. For advanced skiers there’s not much to go at. We never queued for a lift all week!