Difference in matches and mmr

Every time I play a game of ranked the players are between plat 3 and plat 1, but only my top lane rank is plat 2. My support rank is silver 1, my other ranks are all gold 4. Whenever I play any game in any role I get placed against plat 3-plat 1 players. Is there any way that I can play against players that are in the same mmr as my roles? It seems pointless to have a bunch of roles with different ranks if I play against the same players no matter what role I choose.