For Tax Notices - Would like to have a Two Part Field

I have scanned in all of 2014 tax notices and applied a template that includes the Roll # and Legal Land Description (LLD).  I have made the LLD field multi-value, but haven't for the Roll # field yet, even though some of the tax notices reflect numerous different properties on one notice.

Really, what would be ideal would be to have a field that could encompass a Roll # and LLD that were tied together.  Roll #801430; LLD NE-30-041-12-4 on one line, as they will always be tied together. 

Purpose?  If all you have is the LLD, you could search for "NE-30-041-12-4" and when you found it, see the Roll # that is tied to it; then, you could do another search for the Roll number to pull up any documents with that Roll # on it.  A piece of correspondence may mention the Roll # or the LLD, but not always both.

Thinking even further, since every LLD is tied to one Roll #, it would be awesome to have a reference table where if you entered a roll #, the LLD would auto populate and vice versa.

To clarify:  Multi-value settings on two individual fields doesn't really work, because there is no way to know which of the roll #'s are for which of the values in the LLD multi-value fields when the topic of a document includes more than one property. 

Thx, Connie