I don’t understand why the computer is suggesting I move the rook to e1 in this scenario.
The engine thinks that White will soon play exf5. If this happens, a rook on e1 will then be attacking the pawn on e5. (The other rook is needed on f1 because it thinks Black will get a knight on d4, which attacks f3. So it has to be the a-rook that moves to e1.)
This is the line it shows me:
[FEN "2kr3r/Qpp5/4n1pn/4pp1p/1q2P2P/2NP1PPB/PP6/R4RK1 w - - 0 1"] 1. Rae1 Qd4+ 2. Qxd4 Nxd4 3. exf5 Ndxf5 4. Rxe5
This is an about equal position material-wise. The rook on the a file is undeveloped unless you can get rid of the pawn in front of it (which Black should not take) to support the queen, or push it far enough up the board to support an attack.
Otherwise it looks like to me a developing move to get another piece active to prepare a center battle since White doesn't have a queenside attack. This does give away a pawn but after Qa5 everything is defended and the Black queen can try to stick around on d2 but the Stockfish still argues having queens on the board is +4.0 for White.
[Variant "From Position"] [FEN "2kr3r/Qpp5/4n1pn/4pp1p/1q2P2P/2NP1PPB/PP6/R4RK1 w - - 0 1"] 1. Rae1 Qxb2 2. Qa5 Qb6+ (2... Qd2 3. Re2 Qxd3 4. exf5 Nxf5 5. Rxe5) 3. Qxb6 cxb6 4. exf5 Nxf5 5. Bxf5 gxf5 6. Rxe5