Joey, It may do little good to buy the mineral rights under your lot unless it's a large estate. If you only had half an acre and you leased for 25% royalty and production was worth $100,000 dollars per acre 0.5 X 0.25 = $6.250, less taxes, less what you paid for the minerals to get them back and then the payments would be spread out over 10 to 20 years or more. The production may only be worth $50,000 per acre also or may never be drilled and buying your mineral rights back could be a poor investment. Depending on the cost of the mineral rights and what the seller would be willing to sell them for, you could get a great well or even two great wells and still lose money on the deal.
Your ownership of a small amount of minerals rights would not trump the right of others around you to produce their minerals, so there would be nothing to gain there.
Yes it's legal for the developer to reserve the mineral rights. If you owned the minerals rights and you sold your home, you would be able to reserve the mineral rights in the sale.
Joey, owning mineral rights is a good thing in my opinion but I think it unlikely that owning them under your house would be worth the expense and effort to buy them back. I think the same amount of money it would cost you to buy back your minerals invested, could give you a much better return.
If you must own minerals, nothing says they must be the minerals under your home. You could try to buy an acre or acres elsewhere. I hope this helps.