You can launch from a ramp, but it all depends on the ramp. Small beach wheels are big plus...

You need space and time to raise the sails. Meaning you are going to use some ramp space to do so, you need to be facing the wind and other boaters waiting to launch their jet-ski/powerboat/kayaks/dinghies are going to be annoyed by you because they can't launch while you are in the way.

If the ramp is wide, not used by a lot of people at once, with the wind blowing from the top of the ramp toward the sea there is no issue in using the ramp at all. Raise the sails on top of the ramp, and go down with the boat facing the wind. You just need a good set of beach wheels. Once the boat is in the water, keep your boat on a leach while you are packing the beach wheels nearby.

If the wind is blowing the other direction, from the sea, it's also fine as long as the water is shallow enough for you to hold the boat facing the wind without it banging against the concrete. But you need an helper or a crew to give you a hand with the wheels unless you have a way to tie the boat while in the water. Note that if the ramp is not well protected the waves can be a big issue.

A narrow ramp with wind coming sideways is a nightmare: you can't go down the ramp with the sails up and the ramp is not wide enough to park the boat facing the wind to raise the sails...

And then there is the issue of the channel to go out from the ramp. I have not so fond memories of tacking through the harbor channel in Santa Cruz... A hobie 16 with the wind right in the channel axis, boat traffic in both directions, and waves pushing you back: not fun! Coming back is interesting as well, DDW with no way to slow down, I had a nice exchange with the harbor patrol once, they complained I was over the speed limit! I pointed out that in 25 knts of wind DDW, I had no way to slow down and they let me go.

My current club is on a reservoir all made in concrete. Our "beach" is a big concrete slab and we have two ramps on the side of the beach as well for when the water level makes the beach unusable (Map: You can see the north and south ramp as well as the beach). As the two ramps are not parallel to each other we can launch in almost any wind conditions and water level, picking the right ramp based on the wind and raising the sails before going down. (Incidentally the motorcycle and the trailer in the south parking lot are mine, try to find my Stealth on the water: I'm there...)