There are always a lot of questions as to what qualifies as a shelter in the Frozen Otter. I simply define it as something that is large enough to accommodate you and still keep out the rain/snow and wind. This could be a full blown tent, or a simple tarp with means to pitch it. Remember that you will probably already be carrying trekking poles which could be used, and a length of rope does not weigh a ton.
Weather in the Rockies is highly unpredictable. Daytime highs can get up into the 80s and nighttime lows can dip down below freezing. The key is to think in layers and be prepared for anything. Summer usually also brings afternoon thunderstorms, so having an easy way to stay dry is essential. I prefer a poncho for this since it is so light weight and easy to get on and off.