What you are wanting to do is very possible, mostly for those with a lot of launch/recoveries under their belt. It also really depends on the conditions of any given day, and the layout of your boat ramp area.
Your first attempts would be to do it on a day where the winds are not very strong, and not blowing exactly perpendicular to the ramp in either direction. The idea would be to have some cross winds to the ramp so you can sail straight away and straight back. You would set up the boat in the parking lot with the sails up, wheel the boat down the ramp with the downhaul completely out, and the sheets completely out so the sails can luff as much as possible. Roll the boat down the ramp and as soon as you get in the water turn the boat into the wind and have the crew stand in the water and hold the boat there while the skipper takes the wheels back to the trailer and locks them up (that's what we do).
Then, have the crew hop on and get ready to sheet in the jib, then the skipper turns the boat, tells crew to sheet, then the skipper hops on and keeps the rudders turned to steer the boat out, and lock the rudders down when water is deep enough and then start sheeting in the main. When you return, the object is to be going as slow as possible, sheets out as much as you can, then right when you get to the ramp turn up into the wind and have one of you hop off and hold the boat there while the other goes and gets the wheels.
There are places we sail that are basically just boat ramps, and you have to do all of the above. We (Fleet 5) will be having our first club race of the year next weekend on 3/7, you are welcome to come by and we can show you how we set up in the parking lot, roll our boats down to the ramp and launch from there. Here is the website link to the club, its on the southern tip of St. Petersburg, so not sure how far from there you are.http://www.gulfportyachtclub.com/
If you can tell us the name of the lake, and where it is we can google earth it and take a look.
Welcome to Hobie 16 sailing, hope we can help you get the right start.
Division 8 chair