I too have over-spiced roasts/meats. Water alone will not help mask too much pepper as the extra pepper will only flavor the water. You may need to entirely change the flavor profile of the meat. Be careful of how much you have already cooked the meat, as additional cooking time can dry out the meat. Both of the suggestion below should have you fully submerge the meat so that the liquid covers all meat to help re-flavor as well as keep the meat moist. Even then, however, overcooking may still be a problem.
I have found that adding tomato sauce to the roast and letting the roast braise in the tomato sauce, even adding a good cup or two of red wine to the tomato sauce, will help remove too much pepper or spice as the tomato acid can help soften that flavor. However, you will then have to re-season the tomato/wine mix to a flavor base that you prefer through a trial and error method. I use a tomato sauce that has no sugar and low sodium, but use what you like and then adjust for the flavor you prefer with salt, sugar, etc.
Another option is to take the tomato sauce and the wine and create a sauce on the stove top first, and then use this to braise the roast. You can take one or two cups of wine and put that into a pot large enough to comfortably hold the liquid as it boils down. When the wine boils down to half of its original volume, then add the tomato sauce (depending on the size of the roast it may be the entire jar or less) and then, to that, add enough plain yogurt (full fat is best) or cream to create a quick-tomato-cream sauce. The combination of cream and tomato will help mask too much pepper. You can then braise the roast in this sauce. Braise slow at a low temperature, perhaps 275 degrees F, in the oven for a couple hours. in a sealed roasting pot with a lid or a covered roasting dish.
There is no perfect solution, and you indicate you are using a pressure cooker, which I have not used personally so I cannot help with developing a method for that type of cooking. My method is pure braising in a low temperature oven, no more than 325 degrees F for about 3 hrs for a 5lb roast, more or less depending on the size you have.