Yes, mummification remained an important funerary practice well into the Roman period actually, and incorporated Hellenistic, and later Roman, traditions such as death masks and portraits of the deceased. There is of course, a distinction to be made between the Greek speaking populations and the rest of the Egyptian populace in status and customs. While the majority of Egypt continued to practice their religious and funerary customs as they had for generations, the Greek citizens either continued practicing Hellenic traditions or adapted certain Egyptian ones to their traditions, and many of the more well off Egyptians that acquired the Greek language also adopted Hellenic customs, which exemplifies the syncretic nature of the Hellenistic Era which is distinguished by the cultural and religious exchange between The Hellenic world and the Near East. The famous Faiyum mummy portraits are an excellent example of this, they are funerary portraits that were placed over the faces of the deceased, and date to the Roman period in Egypt. The mummies are in all likelihood Greeks or Hellenized Egyptians but the portraits themselves are distinctly Roman or perhaps Graeco-Roman in style and are not attested to before the Roman occupation in Egypt. Another example might be the temples, mausoleums, and necropolei built during the Ptolemaic period that contain mummies, in particular the Necropolis of Alexandria which was one of the wonders of the Medieval world, and Taposiris Magna a temple complex built during the reign of Ptolemy IV that was continually renovated throughout the Ptolemaic period and may even be the final resting place of Ptolemaic Egypt’s final ruler Cleopatra VII. The thing about Alexander’s annexation of Egypt is that it did not dramatically alter the way of life for most Egyptians, particularly those in Upper Egypt or more rural areas, and the Ptolemies were mainly content to allow the people and priesthoods to carry on as they had before (this out of as much indifference as tolerance).