3 lb. lamb roast
2 t powdered coriander
1/2 t powdered spikenard (See below)
Mix spices together, adjusting quantities to your taste. Rub mixture on lamb, and cook in a 325 degree oven for about 90 minutes, or until it reaches an internal temperature of 155 (for medium).
The short medicinal text A Dietary Calendar (appearing in translation in Andrew Dalby's Flavours of Byzantium) mentions cooking lamb in April:
With this take gravy moderately spiced with spikenard, green coriander, and a little pepper, and the fruit of safflower because it relaxes the bowels.It is also mentioned for June:
No spicing is required at all except coriander, spikenard, and anise.I chose thus to use coriander and spikenard because they appear more constantly, salt because it is a ubiquitous addition to roasting meat, and pepper for reasons of taste. In my opinion using anise instead or in addition would be fine as well. Safflower is generally used for its color, as it is not considered to have a very strong flavor. It is suggested here for medicinal purposes, and I don't think that it needs to be obtained in order to achieve the intended flavor.
Spikenard (or simply nard), on the other hand, is an extremely potent aromatic spice, with a scent and flavor that are difficult to describe. I would venture to place it somewhere between cinnamon and catnip, and its application to cuisine is not necessarily obvious to a modern taste. Its flavor is less distinctive than its aroma, but I would still recommend being sparing in its use, as too much could easily give a dish an unpleasantly musky quality that is difficult to construe as desirable. Oddly, when its pungency is kept in check its impact on the dish is fairly mild. If you have some around, you should certainly experiment, but I think the dish can be made acceptably without it.
NOTE: if you do decide to obtain spikenard, make sure that it is Indian spikenard ( intended for culinary purposes, not American spikenard (