I had a similar thing before i left my hometown club (i still live within walking distance of the ground)
I got frustrated at the lack of proper opportunity in the first team, making up the numbers is fine when you are young lad looking for experience, but not for 2/3/4 seasons in a row. Eventually i left for a new club with a first team at a slightly lower standard. We are now in the same league as my home club and last time we played we beat them. I also finished top of the whole league pyramids dismissals charts for keepers in my first year away from my home club.
If leaving for pastures new is not an option, i would suggest making it clear that you will play for the first team if given a fair go in your preferred position. If it doesn't work out after 5, 10, 15 or however many games then so be it. If it doesn't work out or if they don't agree to it, then request to be left to it in the twos. I coach a lot of people who are shot to bits because they serve one role in their second team and then are told to do something completely different when called up into the first team. In the end they are not really doing well at either and become fed up with the game.