Yes, you can download a gedcom of your Ancestry tree but it is unsatisfactory with media getting left behind and various info not coming down the way you expect. The only realistic way to get Ancestry tree info out of the online server right now is if you have Family Tree Maker installed and linked to the Ancestry tree. Once you have the tree info into FTM, RM7 will do a direct import from the file with good results. This will only work with version provided by Ancestry and not MacKiev (the new owners). They changed the file system which prevents direct import by RM7. Or wait until later this year when Roots Magic will be able to release their new version which will support Ancestry trees. It sounds like you have an FTM file somewhere on a computer. If you have the file, RM7 should directly import it with good results. It would be a simple process.
--Long time FTM user