Portugal from 1600 ISOT to 50 AD

  Well its slightly complicated by the fact that technically Portugal and its empire doesn't exist in 1600 as it was annexed to Spain in 1580 and only regained independence in 1640.  As such there will be some Spanish forces present and also during this time period the Dutch were replacing the Portuguese as the primary power in the East Indies, Ceylon and the Cape and contesting their control of northern Brazil.  As such without checking up the details not sure what parts of the Portuguese empire would be brought along.

  Rome is pretty much in its peak and under emperor Claudius so has reasonably decent government although unless its butterflied Claudius dies and Nero becomes emperor in 54AD.  Its in 50AD - although the wiki entry for Nero says it was Feb 49 AD - that Claudius's 4th wife, Nero's mother persuaded him to accept Nero as his heir.

  However I'm doubtful that Rome would conquer the Portuguese homeland, unless there was serious internal problems that allowed this. The Portuguese have much more advanced technology, especially in naval and gunpowder weapons but in other regions as well.  Their going to control the seas which will make shipping forces or supplies by sea, much the easiest way very difficult.  Similarly the close order formations that the Roman legions use could struggle against muskets and are going to be slaughtered by canon, even apart from the shock effect of the weapons.  Also the Portuguese have much better knowledge of the wider world - albeit from a different time - and once they realise some of their colonies have been brought along that will give them additional resources.