What does Paul urge the believers in Rome to do?...

To present their physical bodies to God as a living and holy sacrifice, acceptable to God. This would not be a sin offering but a burnt offering, a consecration offering to establish fellowship with God.

If his offering be a burnt sacrifice of the herd, let him offer a male without blemish: he shall offer it of his own voluntary will at the door of the tabernacle of the congregation before the Lord (Leviticus 1:3).