Does this sound like a reasonable way to slow cook a rib-eye?
The method sounds fairly traditional.

You may find better results doing the oven phase first, and the searing phase last.  By doing so, you will desiccate the outside of the steak, making it begin to sear more quickly (since there is little or no water left at the surface to evaporate).

The pan you use for the oven phase matters very little; cast iron will be superior for the searing phase.

Since you are going for a fairly classic red wine pan sauce, you may wish to investigate butter mounted sauces, rather than doing a roux based sauce.  This may give more intense flavor, but is certainly not core to the technique for the steak.  This Chicago Tribune article has a good summary of the technique.

The one key to success that you have left out is seasoning the steak.  Perhaps the best method is to season it liberally the night before (or at minimum, 40 minutes before cooking), and allow it to sit overnight in the refrigerator.  At first the salt will bring liquid to the surface of the steak, but later it will be reabsorbed, spreading seasoning into the meat itself.  See Kenji Alt's Food Lab article for more details.