The goal when Castelli started work on the ROS Alpha Jacket was to create a winter jacket that is good as it can be for cold days. A jacket offering supreme comfort and breathability, a jacket that can adapt to changing temperatures and conditions. Additionally they wanted a jacket that if you did get caught in a heavy shower or the day turned for the worst, you would make it back home warm and mainly dry. A jacket designed for winter riders with you not having to take a cape out with you. As close to a one box solution as modern fabrics and technologies allow.
Please NOTE The Castelli ROS Jacket is not intended to replace a full shell jacket for prolonged heavy rain. Its a bit like the way a Gabba works (on warmer days) so for 90% of the time its all you will ever need this winter. And for nearly every cyclist that is enough.