Replacements of roof, rain gutters, windows, and furnace on a residential rental property are capital improvements to the structure because they materially add to the value of your property or substantially prolong its life. The items would be in the same class of property as the rental property to which they are attached. Since the property is residential rental property, the items are generally depreciated over a recovery period of 27.5 years using the straight line method of depreciation and a mid-month convention.
New cabinets that are attached to the structure are not considered as furniture. Cabinets and structural components such as furnaces, water pipes, venting, drywall, bathroom, new staircase, etc. - are depreciated over 27.5 years.
Appliances that are not structural components, such as: Stoves, Refrigerators in rental property are depreciated over 5 years. Carpets are also depreciated over 5 years.
Please also see for reference IRS publication 527 - http://www.irs.gov/pub/irs-pdf/p527.pdf
If these improvement expenses are related to changing structural components - yes - they should be added together and depreciated over 27.5 years.
If some expenses are related to not-structural components (carpet, etc) - should be added together and depreciated over the life of that component.
If some expenses are related to repair (painting, etc) - should be added together deducted in the year paid.
If some expenses are related to several types of improvements/repair (design and permit costs, cleaning, hauling debris, etc) - such expenses should be prorated to each type.