Researching a dulcimer I think it is a Bob Lazenby
General mountain dulcimer or music discussions
Dewey -- If you join the Beginners Group as Strumelia suggests (you have to join the Group to see more than a question or two, and to create posts), one of the first things you'll see there is an essay I wrote years ago for beginners like yourself called I Just Got A Dulcimer, Now What? which is an illustrated glossary of terms -- so we all speak the same jargon -- like nut versus upper bridge and fretboard versus neck (dulcimers don't have a neck). It also has answers to many beginner questions about the tuning, playing, care and feeding of your new acquisition.
With your 28-5/16" VSL compared to the Roosebeck's 25.5", you should be alright in using them. The String Choice Calculator suggests .009, .012 and .019 wound for strings where the Roosebeck set has .012, .014 and .022 strings. The calculator usually presents "light" gauges and we often suggest going up one or two gauges from the calculation.
However, I recommend buying at least one more complete set of strings (just to have extras around should you break one during tuning). You can probably find single strings at a local acoustic music shop. I would suggest buying .011. .014 and .021 wound strings. While you're at the store, I also suggest picking up a tube of Peg Dope, a liquid used to help wooden tuning pegs hold their tuning. Not something you use very often, but worth having should you need it; and head-and-shoulders better than any home remedy.
When you get strings and are ready to tune, start a new post over in the Beginners Group, and we'll talk you through the process.