1. There were many Christian believers inside Roman Catholic in Western Europe before the Reformation. One of them may be Thomas A Kempis.
2. There were many Christian believers outside Roman Catholic in Western Europe before the Reformation.
They were dissidents group against or disagreeing with Roman Catholic
3. There were many Christian believers in Orthodox ( Greek or Russian) in Eastern Europe before the Reformation
4. There were many Christian believers in Asia and in Ethiopia before the Reformation, such as in Iraq, Persia, Samarcand area, Mongolia, China, Korea, Japan.
In India they were preached by Apostle Thomas, who may have preached to China as well.
The Oldest Christian monuments in China dates back to 86 AD.
http://www.edessa.com/history/monument.htm
The recent discovery in North Korea tells that there was a Christian community around 200 AD.
Tang Dynasty of China had the Christianity which was the second largest religious group, next to Taoism then. King Tae-Jong himself is believed to be a Christian.
There were 3 times of movement there: 1 century, 6-7 centrury by Nestorian, Eastern church during Mongolian 12-13 c.
5. In Western Europe there were many believers who were persecuted by Roman Catholic, who were called, Cathari, Albigenes, Waldenses, Montanists, Donatists, West German Brethren, etc. They influenced unto Bogomils,Bohemian Brethren, Moravian Brethren etc. after Reformation.
Staupitz was the one who influenced Martin Luther greatly, and was Waldenses.
They didn't belong to Roman Catholic as they refused Mary Worship, Idol making, Papacy etc.
You can find some of the excerpts here:
http://ourworld.compuserve.com/homepages/thailand/PC-B-016.HTM
http://ourworld.compuserve.com/homepages/thailand/PC-B-015.HTM
http://ourworld.compuserve.com/homepages/thailand/PC-B-013.HTM
Above is from Pilgrim Church by EH Broadbent.
I don't agree with the Author entirely as he recognize Catholic Church and Origen quite a lot, but I would agree that EH Broadbent wrote quite reliable Church History.
But one thing clear is that God is faithful and victorious all the time and He preserved His church faithful to the Truth all the time.