Answer:
The Roman Empire that was responsible for a major shift in the dominant religious attitude of the Roman Empire was the Eastern Roman Empire, also known as the Byzantine Empire.
In 380 AD, the Byzantine Emperor Theodosius I declared Christianity to be the official state religion of the Roman Empire, effectively making it the dominant religion throughout the Empire. This marked a significant shift from the previous religious policy of the Roman Empire, which had been relatively tolerant of a variety of different religions.
Under Theodosius I, other religions, including pagan religions and various Christian heresies, were suppressed and outlawed. The Byzantine Empire played a key role in the development and spread of Orthodox Christianity, which remains the dominant religion in many parts of the world today.
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