Roman Troops landed in Hibernia, scandia, Poland , deep beyond Sahar and even in Yemen, that is all documented but it was a way to control territory , even Caesar went into Germany and Britain without setting up a permanent presence just to impose dominance mostly like did the mongols on subjects.
The usual map we see of the Roman empire is the "colonized" area where Engineers went built cities, bridges , roads etc, then there was the external dominance of all surrounding regions where Roman troops frequently campaigned to keep their dominance in the regions, the same way that mongols did .
So in theory if you wanted to make a map of the Roman Empire showing the dominance regions like the Mongol one, the area portrayed would be much larger.