One of Joel's favorite things when he was growing up was when his dad would make a tri-tip roast. And as many recipes as we've received and made our own from his family, this one remains the same, maybe because it's so tasty and so easy.
Tri-Tip roast (ask your grocery's butcher if you don't see it) Dijon mustard
Rub the roast with mustard and salt, don't be stingy with either of them. Cook on your bbq grill until medium. There will be some nice bits on the end that are well done, the whole thing has good parts too it. It's even tasty served cold the next day.