Mithras was the central god of the Roman mystery religion known as Mithraism. Mithras is derived from the earlier Persian Mithra and the even earlier Indian Mitra. However, elements of the earlier mythologies cannot be simply implanted into the later Roman religion. Mithraism was popular around the same time that Christianity was getting popular.
Despite the claims of some mythicists, Mithras was not born of a virgin, did not have twelve disciples and was not crucified and raised. Mithras was born from a rock. The closest to twelve disciples are depictions of Mithras decorated with the twelve signs of the Zodiac. Mithras never dies or is raised in any narrative that we have.