The website says all bags must be checked! I like to carry my DSLR but would not like checking it! Should I leave it at my hotel when I take this tour? Also, how do I make just a reservation for this gallery so that I can get a Roma pass there & use it for admission?

If you don't want to check it, leave it at the hotel.

You can choose to reserve only at
http://www.ticketeria.it/ticketeria/borghese-eng.asp

We just returned from Rome and purchased the Roma Pass. We used it for the Borghese and called from our apartment after we arrived for the reservation. The Rome Pass is a great deal since it includes unlimited use of the metro/bus lines for 3 days, and you must visit 2 of the museums during those 3 days.
We were happy to be able to enjoy the Borghese Gallery without carrying a bunch of stuff. It is a beautiful yet smaller museum and is quite easy to use the check desk. Hope this helps!

Karen

I checked my bag with my DSLR in it. No problem. I didn't want it leave it in the apartment because I wanted it afterward.
They make everyone check all bags, but they will let you keep your wallet. Oddly enough, they do not check coats, only bags.
You can make the reservation online using the link in the post above. You can buy the RomaPass at any of the sites where it's valid, or you can buy it there at the Borghese. However, if they are out, you are in trouble! if you can, buy it before. That way you can use the transportation pass which comes with it to take the bus up to the Borghese. We bought our pass at the castel Sant'Angelo two days before we used it for the first time.

Many museums in europe - esp those with smaller items - make you check anything larger than a wallet (which you keep in your hand). I would;t hesitate to check anythig in a major museum.

There is hardly any museum at all that will let you enter with a bag larger than purse size.

They aren so strict about the "bring nothing in" rule at the Borghese that when we were there they were trying to prevent an elderly gentlemen with an oxygen tank from entering. I was not able to see how the disupte ended, but I didn't notice him in there with his tank.

When I visit the museum I take a small fabric purse that I can wear across my torso and I put my wallet in that. I don't mind checking my bag but I do not like to part with my wallet and this meets their rules.

I was just there a couple of weeks ago. Had my DSLR and a HD camcorder in my bag. I had some reservations about giving it up also before I got there, but after seeing the set up I was at ease. Don't worry about it.

You can purchase the Roma Pass at the airport when you arrive. Go to the right after you exit baggage claim and when you come to the end of the shops there will be a Commune di Roma booth on the left.

Had to do the same thing at Buckingham Palace. I did not like parting with my camera. It was the first time I encountered this, but it worked fine and it was nice to walk around with my camera hanging off my shoulder.