You don't need the math geniuses on the probability forum. You just need Google.
www.math.sfu.ca/~alspach/art8.pdf
Answer: 1/64974.
The 2.5million to one is the chances of hitting a specific suit of royal flush given exactly five cards. Hitting any royal is 4x more likely. Then make it 7 cards instead of 5 and it's not that unusual. The requirement that the player has to play two in hand pushes the odds back up a bit.