Most photometric charts don't extend so high, so I created one for this type of job: download chart
Don't know your steeple height and width, but it looks like you might needs a 12 degree.
To calculate the footcandles, use the formula:
Center Beam Candle Power (CBCP) divided by distance squared.
Typical CBCP for MR-16 lamps:
20W, 12 degree: 3,300
20W, 24 degree: 1,400
35W, 12 degree: 6,100
35W, 24 degree: 2,500
50W, 12 degree: 9,000
50W, 24 degree: 3,000
Your target footcandles depend primarily on ambient light and other illuminated objects nearby (including the tower beneath). It also depends on the specularity and color of the roof, and on whether or not you want this roof to be a visual destination (probably do). I would say your target range is 5 to 10 fc.
With that in mind, you might want to really punch the light - 50W, 12 degree or, preferrably, (2) fixtures 35W, 12 degree.