More than likely, walking on the roof did not hurt anything. If you heard cracking or popping from the weight under-foot, it probably still did not hurt anything. They are designed to take some weight, otherwise all of us would have problems with winter snow weight. But you definately do not ever want to have a party on the roof!
The veneer probably will not hurt anything. What you will want to watch for is the refrigerator. Like at your home, if the freezer or refrigerator is not sealed tight, it let's air in. Air and moisture causes condensation. In your freezer it causes white ice to build up on the wall. When the unit looses power, that all melts back to water. If the seals are not tight any more, the same place air and moister came into the refrigerator/freezer is the same place the water will drip back out. Clean the seals real good around the refrigerator and you'll probably be OK. Just be mindful of potential ice/water build up and you'll be fine. We alwasy wipe our camper refrigerator out when we turn it off.
If your tires look good, they are probably OK. If not dry rotting (crack in the side), you're ok. I'd think about changing in the next year or so, just to ease your conscience.
Insurance? There's so many variations it's crazy.
But typically, when the camper is in tow, it's covered by your automobile policy if your camper causes damage to someone elses property, like if you BACK into another car and damage the other car. You're automobile policy will probably not have any kind of replacement on the camper. You'll need to get that worked into your policy with your agent.
You'll need to, or should, carry a separate policy for the camper, usually a rider on your automobile policy to cover the camper when it is not in-tow.
Now this get's interesting also, because some home-owner policies cover the contents of your camper (or your contents wherever you may be anywhere in the world), and some do not. Here again, check with your agent.
You (should) make sure you have coverage for all of the following scenarios:
1. When in-tow, if your camper is the cause of an accident, all parties involved are covered.
2. When not in-tow, (parked and unhitched), you are covered for any damage that could occur to the camper ... fire, tornado, tree branch falling through the roof, vandalism, theft of the camper or anything on the camper that's part of the camper.
3. Contents inside the camper (your personal stuff), in the event you have a break-in and something gets stolen. This covers televisons, computers, guns, that T-bone steak in the freezer and bottle of wine!
4. And something that most folks don't think about, a liability in the event anyone get's hurt (slip and fall for example) when inside your camper, or outside! Yes... outside. If someone trips over YOUR garden hose you could be held liable for the broken leg, not the campground because YOU were neglant NOT the campground. Has this ever happened? I've never heard of it, but it's possible and we made sure in all our policies combined, somewhere in there we've got this covered also.
Good luck. Hope my ramblings help!