Asked for lamb arm cut, got it in slices, are these still good for roasting?

lol it turned out a little dry, but probably just because I'm not very familiar with the roasting technique (asian family here, I'm in high school and just starting to try western cooking). Family said it was decent but i thought it was a little unbearable, maybe next time :p. thank you all for your answers!

i marinated some lamb steaks (leg of lamb slices with round bone in) and then grilled them. they weren't as tender (duh) as if they had been slow roasted. with the leftovers i slow simmered in some marinara sauce and served over pasta and that made them really quite tender. i'm not sure it is a cut i would try again unless i braised them or cooked more slowly than the grill.

This recipe, from The Classic Italian Cookbook, is for braised lamb, so it won't dry out. I would just be careful not to cook the pieces too much in her step 2, where she tells you to brown it well on all sides. Cut back on that. Then, simply stack the pieces on top of each other for step 3, where you cover it in white wine. From there, the cooking may proceed more quickly than the 1 1/2 to 2 hours she suggests, but maybe not all that much. As she tells you, you'll know when it's done, because the meat will be very tender. Overall, I don't think this is a big problem, I think you'll have a delicious dinner.

I'd marinate and grill those slices...here's a recipe that calls for loin chops but I've also done this with blade or round bone chops:
https://food52.com/recipes/12119-grilled-lamb-chops-greek-style

Well, I've never ran into this situation (nor have I read the specific recipe you are working from), however you might be able to tie it up with twine and proceed with the recipe. Note that your goal is to hit a certain internal meat temperature. Cook meat until it is done, it's not about the clock on the wall.

That said, the slices will allow the heat to penetrate and cook the meat faster, so two hours will probably be overdoing it.

Next time, give more explicit instructions to the butcher or find a new one.

Good luck.

Are you able to share a photograph?

Normally sliced meat will cook very quickly; something thin may dry out quickly.

for future reference, if this happens again, what if i were to tie all four pieces back together with cooking string (and just throw some spices in between the meat slices)

I'm making a recipe from Marcella Hazan's book: Roast Spring Lamb with white wine (something like that).