Milk-fed lamb isn't as "gamy" as lamb when it gets a little longer. While rosemary and garlic would be very good, you don't need to go that strong. For instance, salt, pepper and thyme would be just fine. Something else: Of you've already had and cooked rosemary/garlic frequently, you might be ready for a different approach.
How about splitting the difference and going with a milk-fed lamb leg preparation typical of the French and Spanish sides Pyrenees region, gigot d'agneau anchois (aka pierna de cordero con anchoa)? It's a classic of French cuisine, but one I first had in Spain.
Take the fillets from a can of anchovies, drain them, refresh them in good olive oil. Separate the fillets and cut each one in half. Cut a couple of cloves of garlic lengthwise into spears. Stab the lamb all over with the point of a knife. Jam a garlic shred and a piece of anchovy into each whole so the tip of the garlic just barely peeks out of the lamb. Fold the extra length of the anchovy slice back over itself and stick it on the garlic. If the anchovy breaks into pieces when you try to get it in the hole, just stick it on top of the garlic.
Wrap the lamb tightly in cling wrap, and refrigerate overnight.
Heat a 1/4 cup of very good olive oil, and saute a three or four sprigs of thyme in it.
Unwrap the lamb, put it in a closely fitting roasting pan, and pour the oil over it. Push the thyme sprigs into a corner of the pan. Season the lamb on all sides with salt, freshly cracked pepper and paprika.
Remove the lamb from the pan. Slice an onion into six even slices, and place them on the bottom of the pan to form a rack for the lamb. Place the lamb on the onions. Cover the roasting pan with foil.
Roast the lamb in an oven preheated to 325 until just medium rare, 120F - 125F internal.
While the lamb is resting, prepare a sauce.
Remove the onions slices from the pan. Put the roasting pan on the flame. Add some water or wine to the drippings, scrape the fond into it, and cook until the fond is dissolved. Remove the sprigs. If you like, you may puree one or two of the roasted onion slices and use them to thicken and flavor your sauce. Alternatively you may chop them and use them for garnish, or simply throw them out.
Edited by boar_d_laze - 3/28/13 at 4:35pm