Yes, a direct vent gas fireplace can be put anywhere in the house if the vent lengths and turns meets the rules of the manufacturer which are shown in the form of charts & diagrams in the installation instructions. It can vent horizontally to an outside wall or vertically through the roof within those rules. The roof termination would be an exposed metal pipe. Fresh/combustion air is drawn into the outer wall of the vent and the center pipe acts as the exhaust for combustion byproducts. A B-vent gas fireplace can only vent to the roof and draws combustion air from the room (or through a separate outside air duct). It can have a glass face or bi-fold doors. Either unit might have heat recirculating louvers or not. If you find the roof termination unattractive you can add a fake masonry or wood surround. Roof leaks shouldn't be an issue if the roofer knows how to flash a roof penetration. Be sure to use Ice & Water Shield self-adhering flexible flashing in addition to the factory metal flashing. Click on one of the direct vent gas fireplace installation manuals and see if the vent tables will work for your installation. It's a lot of design work if the vent travels horizontally and vertically. Here is a link that might be useful: installation manuals

Thanks for your input, Renovator8. That fireplace has been through a few transitions. It was first an Isokern masonry like fireplace but to save some money we changed it to a b-vent on the plans. Once we placed the house on the lot, it became apparent that the b-vent pipe would be viewable from the street, and would have to be fairly high due to the slope of the roof. The initial hope was to hide the b/vent pipe from view behind the upstairs Isokern chimney, but the house is oriented in a way that it is viewable on approach, even though not seen in the front or back yard. We then changed to an direct vent. The whole reason for the direct vent was to not vent to the roof, so I would like to avoid that. We have a couple of options with the Montebello like running them behind a bookshelf in the dead space and then over a boxed bay bumpout, but the pipe is so big it may make it not feasible. I don't think we have enough rise available to run it over the master bedroom tray ceiling above, unfortunately, because that will vent out the side of a house above the a/c in a very inconspicuous place.

When we were shopping for a gas insert 3-4 years ago, we had the good fortune of seeing several systems in operation. We selected a Jotul direct vent insert because we wanted real serious heat, and we're very satisfied with it, although it does not produce really dramatic dazling dancing flames that make you say WOW. But we saw one vented gas insert that in our opinion produced really terrific flames. The brand name is Eiklor. They have a website. If you call their 800 #, you might get old Mr. E himself. Of course he talks up his system as the best thing since sliced bread. Check out the website site. I would caution you about this sytem, based on my own estimation -- it probably uses a whole lot of gas, and most of the heat goes up the chimney. Mr. E will probably take exception to that assessment. I leave it to you to decide. But if your primary objective is a really dramatic flame, and you do not care about the expense of high gas bills and most of the heat going up the chimney, you will probably like this sytem.

Keep shopping there are many brands to choose from. Look at Mendota, Regency and Iron Strike are to name a few quality brands w/ great warranties and models to choose from.