After a failed assassination attempt in 155 BCE, the ruler of the Cyrenaica, Ptolemy VIII Physcon, announced that he had bequeathed his realms to the Romans. This, he hoped, would be some kind of insurance against future attempts on his life. The text of the inscription is here.
It took some time, however, before the Cyrenaica became a province, because Ptolemy had a son who succeeded him; this Apion had to repeat his father’s promise, and almost eighty years after Ptolemy had announced his will, the Romans accepted the kingdom in northeastern Libya. They might have seized it at an earlier moment, but being occupied with wars in Spain, Africa, Numidia, Macedonia, Greece, Transalpine Gaul, Anatolia plus a civil war between Marius and Sulla, they had other things on their mind.