I have a 7lb triangular shaped sirloin tip roast 5" at its thickest. I would like to cook it at 135 degrees but I’m not sure how long.
That cut of meat was invented by mean-spirited butchers just to frustrate SV cooks like yourself.
Are you sure you want a roast? When cut into one-inch thick slices it will make a dandy Pot Roast or pound the heck out of those slices with a clean golf shoe with spikes, or whatever, for Swiss Steak or even Chicken-Fried Steak.
If it is run-of-the-market grocery store beef it’s likely USDA Select or Choice with minimal aging. It will be a pretty solid example of beef as throughout its life that muscle kept the animal’s belly from dragging along the ground.
If you still aim at having a roast i’d give it 24 to 48-hours, plus a good sear for flavour. It will be edible, maybe even enjoyable if you pack some coarsely ground black pepper along with woody herbs like thyme and rosemary around it. There’s no need for any longer cook than 48 hours unless you want to go for pulled beef.
Next time you’re meat shopping do yourself a culinary favour and select a more uniformly shaped cut of meat.
Here are a few links that you might find useful:
Whatever you wind up doing, let us know, and how you make out. Good luck!