Really? Romans are quite human, and it doesn't require disfiguring the entire globe of Toril to introduce them. I'll tell you what got me started on this. Just look at the two pantheons above. The Roman Pantheon consist of the following:
Roman God -------------------------- Faerunian equivalent
Juno the goddess of marriage
Jupiter the God of Rulership (Possibly Ao, but Jupiter takes a more active hand)
Vesta the goddess of home and hearth
Neptune the god of the sea: Umberlee
Pluto the god of the underworld: Kelemvor
Ceres the goddess of agriculture: Chauntea
Vulcan the god of craftsmen and the forge: Gond
Mars the god of war: Tempus
Diana the goddess of the Moon and hunting (Also Hekate): Selune for the Moon, Mielikki for the forests, Mystra for Magic, Sylvanus
Apollo the god of the Sun, Music, Healing, and Prophesy: Milili for song and poetry (No god of the Sun or prophesy)
Minerva goddess of war, crafts, and wisdom: Oghma
Mercury the goddess of trade, thieves, and travel: Mask for thieves, Akadi for movement, Waukeen for trade
Bacchus the god of wine
Venus the goddess of love and beauty: Sune
Notice something? Faerunian deities tend to be more specialized. Also the Romans don't have a god of Murder, There is no Faerunian god of the Sun. In the Roman Pantheon Neptune is a greater deity while Umberlee is a lesser one. Diana and Apollo have large portfolios covering many areas, they are twin brother and sister after all.
Apollo doesn't have much competition if he were to enter the Forgotten Realms, it has no Sun god after all, and no god of Prophesy either. Venus and Sune are rivals. There is not a forgotten realms equivalent for every Roman god, nor is there a Roman equivalent for every Forgotten Realms god. Minerva is more good aligned than Oghma, and she has wisdom while Oghma is just a god of crafts and invention.
One thing I should add is that the Roman Pantheon was an actual pantheon of gods that real people worshipped and believed in, while the Faerunian deities are made up for a role playing game. Another advantage the Roman and Greek gods have is they come with a series of stories and myths, the Forgotten Realms gods just have portfolios, and a few novels in the present time. The Roman and Greek gods are also more familiar to most people as well. You talk about Mercury and most people know who he is and what he does, that is an advantage in a role playing game.