If you have a cheap red wine or beer you can marinate the roast in the fridge for a couple of days. Cover your roast half way in the wine, after a day roll the roast and get the other side. This process tenterises your meat and flavors it.
Add the roast + wine to your slow cooker and a cup of worcestershire. Cook on low for 6 - 8 hours, until done. This makes a really great flavor roast and gravy, or save the drippings to add to your next pot of beans or lentils for that good meaty flavor. The hungry ones in your family will start requesting your lentils as much as they do your roast.
And my favorite rib recipe also marinates in red-wine + brown sugar and worcestershire - these flavors are soooo good - yum! I add extra brown sugar when finishing the glazing in the
oven.
I never thought about tomatoes, what a great idea Leah, I'm going to try that.