Buddhism (Kalmyk and Buryat peoples in Russia), Shamanism (small Siberian native groups), Zoroastric religion (group in in Azerbaijan).
Belief in One God.
If by belief you mean religion, the Romans had their own religion. Like most ancient religions, it was polytheistic, it had many goods. As for the empire, the conquered peoples had their own religions. The Romans respected their religions and allowed their worship. Apart for Judaism, they also were polytheistic.
The cross
There is no one single characteristic that sets Christianity apart from other religions. Christianity is monotheistic, but so are Judaism, Islam, Sikhism, Zoroastrianism and other religions. Christianity shares the abrahamic God with Judaism and Islam. Christianity was largely spread by imperial edict and conquest, but the early spread of Islam has many parallels. Christianity teaches high moral principles, but so also do other religions. In Christianity, Jesus came to earth and was born of a virgin, but virgin birth was common among the ancient religions. The Zoroastrian Saoshyant, who will also be born of a virgin, has many parallels with Jesus, but has not yet come to earth. The Christian Jesus was crucified, but again, there were other gods, goddesses and demigods who were crucified. Perhaps the one thing that sets Christianity apart is that it is the dominant religion of the powerful and prosperous West. This provides for some a sense that Christianity was destined to dominate the world.
Christianity and Islam both find Israel important to them. Most Christians are willing to abide Jewish control of the region; most Muslims are less willing.
The main religion is christianity.
India has people from many religions, including Hindu, Jain, Buddhist, Islam, Sikh, Christian, Judaism, and ZoroastrianismThe CIA World Factbook has the following statsistics from the 2001 census:Hindu 80.5%,Muslim 13.4%Christian 2.3%Sikh 1.9%Other 1.8%,Unspecified 0.1%
From Wikipedia: "About half the population of Madagascar practices traditional religions, which tend to emphasize links between the living and the dead." - But note the plural; these might be considered to be more than one religion. Apart from those, the largest religion seems to be Christianity.
Each of the ethnic groups in the empire had its own religion. Apart from Judaism, they were all polytheistic. there were rituals to honour the various gods and goddesses which involved offering the divinities sacrifices to appease them. Natural disasters were thought to be caused by the wrath of gods who had not been honoured
The religions are made to make apart the human race from the only religion that is human being. To bring the destroy of the earth as soon as possible.
Muslims, Hindus, and Sikhs
Belief in more than one god is called polytheism. Apart from the related religions of Judaism, Islam and Christianity, nearly all the rest of the world's religions are pantheistic. These include Hinduism, Confucianism, Buddhism, Taoism and Shintoism.