I don't know about the lower-case Roman numbers, but you can do upper case easily. Insert a section break between the pages where you want the number style to change. Click in the first section and Insert tab, Page Numbers, Bottom (or wherever you want them). Then Page Numbers, Format Page Numbers and pick a number style.
Click in the second section and the same drill except when you format the numbers, choose 1,2,3 format and tell it to start at 1.