Actually, the marinade is almost identical to the one my uncle uses (though he uses only 1 bottle of wine). We've cooked wild boar, venison, moose, bison (buffalo) and a lot of other game this way. The best way we've found to cook the meat is on a rotisserie using indirect cooking at about 300-350Â°F, but it's excellent cooked indirectly as well, and if the roast is small enough you can even cook it directly as you would a tri-tip as I showed in this thread:
Incidentally - the whole idea about frying or browning the meat before cooking it actually has nothing to do with keeping the juices in the meat. Browning the meat only serves to build up a bit of a crust and improve the taste of the meat - exactly like searing a steak. If you're using a rotisserie or using indirect heat, skip the above step as the meat develops a great crust without pre-searing.
In addition, it's better to leave the meat on the cookinig grate and put the drip pan under the grate, rather than leaving the meat in a roasting pan. You still get a lot of jiuces in the drip pan, but since the meat isn't soaking in those juices it develops a really fine crust all around the roast as well. Of course, if your meat is on a rotisserie that's not a problem as the meat doesn't sit in the juices, but the crust develops nicely even if the meat just sits on the cooking grate too.
Sorry if I'm going on a bit here, but one of the things I don't like are roasts that have a nice crust on top but are soggy and grey on the bottom because they sat in the meat juices too long.