I would expect genetic studies of Scotland would show up as primarily as Scots followed by Irish, Norse, Normans, and lastly by Germans. This can be derived from genealogical means. I would not expect Romans in the bloodline. They built Hadrian's wall to shut them out.
My complaint is that a genetic study of Britain as a whole is defective. The area now called Britain had varying histories of conquest in England, Scotland, Wales, and Northern Island. Would one expect more German genes in the English than in the other areas? I would. Why tell us only about the 30 percent. What is the 70 percent?
Seventy five Percent of the DNA in Britain today arrived there 15,000-7,500 years ago.
My dad's mother (Mrs Smith, my grandmother) had mtDNA U5a, the same as 9,000 Year-Old Cheddar Man
(BTW, Cheddar Cheese takes its name from this area)