Rome has two Top 20 wildcard spots, so if Venus and Vika request them, they have to be given. Stosur and Zvonareva also qualify for Top 20 WC, but I imagine the tournament would choose Venus and Vika over them.
Each non-Mandatory Tournament receives two (2) “Top 20 Wild Card” spots, which can only be used by Top 10 Players, players with a singles ranking of 11-20 at the end of the preceding Tour Year (“Top 20 Players”), past Grand Slam singles champions, past WTA Finals singles champions, past Premier Mandatory tournament singles champions, and/or former WTA No. 1 ranked singles players as follows:
(a) For Premier 5 Tournaments, if a Tournament’s Player Commitment Formula has not been met prior to the start of the Tournament, the Top 20 Wild Card will be first used by the WTA to move a Top 10 Player into the Main Draw of the Tournament to satisfy the Player Commitment Formula, no matter what the player’s ranking. If the WTA does not use the Top 20 Wild Card, the Tournament Director may award the Top 20 Wild Card to any Top 10 Player, Top 20 Player, past Grand Slam singles champion, past WTA Finals singles champion, past Premier Mandatory tournament singles champion, and/or former WTA No. 1 ranked singles player. If the WTA and the Tournament do not use the Top 20 Wild Card(s), the Wild Card spot(s) revert(s) to the next player(s) waiting to get into the draw.
Konta is also eligible for that WC as Miami champion. Obviously she'll probably get in as second ALT but worth noting.