The Digital Library at the University of Heidelberg is a little difficult to use at first. But if you go to the search page and enter “romae”, you will get a list of books. If you click on one of these, such as Montjosieu’s Romae Hospes (1585), you will get the “home page” for the book, with its link for downloading PDF’s. Page down, and you will see a list of sections of the book, all clickable. Choose one – any one – and click through.
This will give you a single page: but hit the “Vorschau” link at the top, and, le voila, you will get thumbnails of all pages! This is incredibly useful, when looking for early prints. It saves the necessity to download the PDF in most cases.
In this case we find another depiction of the Vatican obelisk and the Vatican rotunda to the south side of Old St Peter’s in Rome, on folio 10, here. It doesn’t give us more than Dosio, but it does confirm it.
For me this settles it: the UB Heidelberg is now, officially, a really important site for anyone interested in ancient Rome. If you don’t take the time to familiarise yourself with it, you are certainly missing out.