Is there a roster of Co A 10th Inf Battle of the bulge at Ardennes France in 1944-1945?

Yes

Edit: Morning reports and rosters for infantry companies are in the National Archives. You can contact them (nara.gov) and ask very nicely, and if you are extremely lucky and your request is assigned to a knowledgeable person who feels like exerting the effort, you might get them to send a copy. You'd want to narrow the date range, because there were changes to the roster of a company almost daily. Typically, this is the sort of information you have to ferret out yourself with an in person visit to the Archives. From the archives you can also request, using the form obtainable from their website, the personnel records of individual soldiers. These are confidential for seventy-five years after discharge, but if you set forth some good reason for asking, such as the records requested are those of a family member, they will send them. Sometimes they charge a fee for copying. The 10th Infantry was one of the three infantry regiments in the 5th Infantry Division. Probably every US division, and some regiments (which were smaller subdivisions) published histories right after the war, usually through the Infantry Journal Press. These are long out of print, but can be found from time to time on eBay, not inexpensively though. Some have been reprinted by Battery Press, of Nashville, Tennessee. However, typically these unit histories will not include a roster of every man who served in the unit. There is usually a Roll of Honor of those killed, and often a list of those who were decorated, and those lists usually mention the company assignment of the individual soldier. But, once you have nailed down the dates the person you are researching was with the unit, these unit histories offer the best easily accessible source of detailed information about the day to day operations in which that individual took part. Much easier than seeking out After Action reports by company officers, which again usually has to be done in person at the National Archives. Most of these unit histories rely extensively on and quote verbatim from those After Action reports. Company A was one of the three rifle companies (also called line, or letter companies), A, B and C, which with Heavy Weapons Company D made up the 1st Battalion of the 10th Infantry. (Shorthand: A 1/10). If you're researching a family member I urge you to persevere. The ffort will be worth it. Best of luck.