How did the role of women change during the high middle ages?

During the High Middle Ages, women began to have a more important role in society partly because of the Church's endorsement of marriage as a sacrament - i.e. an outward sign of a spiritual truth through which God reveals himself. This idea of marriage as a sacrament was really propounded upon by Saint John Chrysostom, who even went on to say that marriage was what holds society together ("Homily on Marriage"). Of course, Saint John was...

During the High Middle Ages, women began to have a more important role in society partly because of the Church's endorsement of marriage as a sacrament - i.e. an outward sign of a spiritual truth through which God reveals himself. This idea of marriage as a sacrament was really propounded upon by Saint John Chrysostom, who even went on to say that marriage was what holds society together ("Homily on Marriage"). Of course, Saint John was significantly earlier than the high middle ages, but during that time period, churches were the central guiding force within the towns and therefore set the tone for the way life functioned.
Additionally, the rise of convents and monasteries was at its height during the middle ages and that also gave women a new high place in society which was formerly reserved for men. Although women had taken vows of celibacy very early on in history, it wasn't until the middle ages that they began to practice monastic aestheticism, which is what has led to modern monasticism. The rise of female monasticism in both the eastern and western world also led to the rise of female sainthood, which furthered the reverences place of women in the church.
In the political sphere, the middle ages had a number of empresses, especially in the eastern empire, come into power. In The Chronographia, written by Michael Psellus around the twelfth century, five out of the sixteen rulers he discusses were women. Although the rulers Psellus discusses ruled during the earlier middle ages, the trend did continue throughout the period, giving rise to a new area of life for women: politics.
So, although women's station was certainly not up to 21st century standards during the middle ages, the time period did bring about a more reverenced place for women in society through both the church and the state.

If you're interested in reading more about women in power, check out Women and Power in the Middle Ages by Mary Erler and Maryanne Kowaleski. It's a great read.