"Roaming" should never happen as owners should have their dogs leashed or under control. Roaming refers to an intact male getting the scent of a bitch in heat and searching for her and any others in like state. A bitch in heat is inticing!
Most will a male should reach full height and begin to fill out before neutering. Years ago, it was done at 6 months. Now the trend is more towards 12-18 months. Do what's good for you.
Egad! I can't believe with all that has been written and reitterated, over and over, that folks still go to dog parks.
Speaking for myself, one problem is this: Not everyone innoculates their dogs adequately. If you have a younger dog, parvo is still a great risk. Did you know that the virus is still there up to a year later in dog poo left on the ground? You wouldn't even recognize it anymore! It would have been beaten and weathered into dirt.
Another: While you may have well controlled, well behaved dogs who understand "play," the person next to you may not! They may be a complete idiot who thinks it's macho to have his male hump every female in the park! It's RUDE behavior. It's an attempt at dominant behavior...as probably not females there are actually in heat.
I've seen dogs who bully others, steal toys, run others down...people included. The owner does nothing.
Dog parks are a lazy man's way of exercising a dog. I enjoy seeing my dogs run and play. We went to my firends house in the country. I knew her, I knew her dogs from classes. They were innoculated. They understood play. In recent years, I've afforded myself a semi private fence. Within it I still have my exercise kennel.
Before that it was clases, hiking, boating, exercise parks for humans...dogs allowed. There are soooo many ways to exercise your dog with out resorting to a exercise park...at least for me!