Any ideas to ensure that me beef roast will be tender tomorrow night?

If your cut of beef is a eye round, rump or one of the "tough" cuts the best method of cooking is a long and slow braise process. As suggested by many, first bring it to room temp, season well, and brown on all sides in a heavy oven-proof pot with a lid. When browned remove to a plate and hold, as you add to the pot onions, celery and carrots. Soften veggies, loosen "brown bits" from pan bottom, then add 1 quart stock (chicken) to pan and bring to boil. Return meat and any juices to pan. Cover and place in 350 oven for 2 to 3 hours. About half way through braising process, turn meat so that each side gets equal time in braising liquid. When done remove from liquid, tent to rest. Use braising sauce to make a delicious sauce to service with the tender beef.

It's not to late I made a pie and the mrs made pasta so the roast will be for tonight. Thanks guys!

Probably too late to be of help now, but I have two tools that to me are indispensable. I use an "injector" to give the roast an internal brine. And then I depend on my Thermapen for an "instant" read on internal temperature. It's possible to argue back and forth on when to raise or lower oven temperature but the simple truth is that no two ovens are calibrated exactly the same (even if they're the same make). Your one true guide to doneness and rareness is the instant read.

Start with the meat at room temp. Use your favorite rub and start roasting at lower than normal temp. Use a thermometer to gauge inside meat temp. For med rare middle once the temp gets to 135 turn the oven up to 500 for 5-10 minutes to create a nice crust. Take it out and let it rest 10 min so the juices can redistribute. When resting it will rise another 5 degrees giving you some pink in the middle with a nice crust

First bring it to room temp for an hour or two (depending on size/weight). In an ovenproof pan coated with olive oil, sear on all sides salting each just before you place it in the pan/turn it over. You're trying to create a nicely browned surface that will contribute to beautifully caramelized meat flavors and pan drippings. Add a couple of quartered onions, 3 or 4 peeled carrots cut into 1" pieces along with the same number of stalks of celery cut the same and transfer the roasting pan to a 300-325 degree oven and roast gently until it reaches an internal temp (at the direct center) of 125-135 degrees, depending how rare you want the center to be. Remove from the oven. Transfer the roast to a platter or cutting board and cover with foil and a good heavy towel. Let it rest for 15-20 minutes so that the muscle tissues can relax, letting the fluids roaming around on their outsides to re-inflate the cells lending that juicy tenderness. Have you ever cut into a roast (or turkey, or chicken) and had fluid gush out? You haven't let it rest adequately. The moral of the story is: please don't overcook it and by all means let it rest before you slice it. You'll do great!