Dispersul is the trade name for a sulfur garden amendment. You can use any garden sulfur to lower the PH although some formulas will work faster than others. Boron is a trace element so you don't need a large amount of it. Google "Boron" and "Dispersul" or "garden sulfur" for sources.
Some garden fertilizers contain trace elements. Find one and check the contents to see if Boron is listed

borax has boron in it, but like karl said it is a trace element, and too much will do far worse damage. rose tone has it, and i'm sure most complete fertilizers, just look on the label.

My soils book list the 3 following sources of Boron to use in your garden: (1) Borax (sodium borate) (2) sodium pentaborate & (3) Boron frits. They also added the following warning: "Since the amounts needed to treat deficiencies are so low (only .0009 to 0.3 lbs/acre!), and since only slightly larger amounts can kill sensitive plants, be careful. Consult your County Ext. Service or other professional before using chelates or other sources of individual micronutrients. Follow directions carefully."

As to Sulfur, I have that deficiency in my soils & I have found that adding lots of organics--compost, manure, & wood chip mulches corrects that problem without messing with my pH.

Boron is readily available in many complete fertilizers with micronutrients. It will take only a few year's application of micronutrients to supply more than enough. Our local Home Depot sells Dynamite Plant Food Plus Minors. Ironite has Boron. Ironite Plus has Boron and other micronutrients. OSH Superfine Rose & Flower Food has Boron and micronutrients. You can search for locallly available brands in this nice database. Boron is not hard to find. Presumably you need sulfur to buffer the high pH. Anything else? Anything you need to avoid?

Here is a link that might be useful: Calif Dept of Food & Ag Fertilizer Inspection Svcs

You can buy Dispersul at Bakers, Berridges, A&P (I think) and Gardeners World for sure. Harpers probably has it, as does Summer Winds, if you're in the Valley. Not sure about areas outside of Phoenix.

You can throw a handful of 20-Mule Team Borax around your rose bush once a year. It's water-soluble. Haven't tried it yet but other rosarians have and haven't noticed any problems. Don't keep adding it, though, just maybe once a year. Our alkaline clay soil always needs chelated iron so we add that 3x a year during the active growing season.

This is also the time to add some triple super phosphate directly to the root zone, along with the Dispersul and a little organic rose food. Added right after pruning, this mix will help you get some nice healthy bushes.

Which soil lab did you use? Inter Ag?