Just brute force, but it works

RollerCoaster.hs

import Text.Printf

-- Should be in some library
blockBy _ [] = []
blockBy n xs = ys : blockBy n zs where (ys, zs) = splitAt n xs

main = interact $
           unlines . 
           zipWith (printf "Case #%d: %.0f") [1::Int ..] .
           map (\ [[r,k,_], xs] -> solve r k xs) .
           blockBy 2 .
           map (map read . words) .
           tail .
           lines

solve rounds seats xs = loop 0 rounds maxGroup seats (cycle xs)
  where maxGroup = length xs
        loop :: Double -> Int -> Int -> Int -> [Int] -> Double
        loop  t  0  _  _ _                 = t
        loop  t  r  0  _ q                 = loop t       (r-1) maxGroup seats q
        loop !t !r !g !k (x:q) | x <= k    = loop (t+fromIntegral x)   r     (g-1)    (k-x) q
                               | otherwise = loop t       (r-1) maxGroup seats (x:q)