The Praetorate was a body that existed within the Romulan Star Empire.

This organization within the Romulan government possessed the most actual power and consisted of members from both the military High Command as well as civilian heads. It served as both the executive branch and as the judicial branch of the state with its main duties including the implementation as well as the enforcement of the laws passed by the Imperial Romulan Senate. At times, the Praetorate was also allowed to propose legislation for the Senate to consider and had the final veto on all military decisions passed by the Senate. The head of the Praetorate held the position of Head Praetor and was the highest ranking member in the Empire.

The body consisted of Twelve Praetors of various positions but by the time of the 23rd century, power had been concentrated into the hands of three of its members. The actions of this group led to Commander-General Ael t'Rllaillieu rebelling against the Empire in order to depose of the Praetorates corrupt leadership. (TOS novel: Swordhunt)

This contradicts canon elements which showed that the Praetor of the Romulan Star Empire was a singular title for the head of state. Its possible, however, that either the government had changed by the time of TNG or perhaps the Praetorate was instead the office of the Praetor.
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