Do you sell inline skates? Do you know of anywhere in Lancaster that does?

Yes they have a skate shop.

Yes you can buy a pair at the castle they cost about $60. When you walk in they will give you a choice to rent or buy them.

They have a pro shop with lots of skating accessories.

yes

Since, the topic is in the Castle Roller skating, the castle sells inline and quads. I have no idea if you can buy them at any stores tho.