Complex sentence: In the imperial provinces, the emperors appointed governors who held the title of "legatus Augusti pro praetore", or pro-praetor, regardless of what position they had held previously.
Split into simpler sentences: In the imperial provinces, the emperors appointed governors who held the title of "legatus Augusti pro praetore". There governors of the imperial provinces were called pro-praetors, regardless of what position they had held previously.