After going over the rules reference I have a question.

Are dice that result in modifiers included in the total value of your start of game roll off to determine which battlefield will be used?

If they are included, do they require a matching non-modifier symbol on a different die to be considered in the total value?

Yes to the first, no to the second

I'll be interested to know how others interpret this but the Rules Reference states to add "the white numbers." So I have always interpreted it as you do include the modifiers regardless of what the other dice show.

The Modifier is the "+" symbol only, a Value is the number.

So a "+2 " consists of:

The "+" Modifier

The "2" Value

The "Melee" Icon Symbol

It took me a while to work it out as the Modifier rule seems to point to the whole dice face.

Anatomy of a die is found on page 8 of the Rules Reference Guide.

Value: The value is a number that is listed above the symbol. (Blanks and specials have no value printed on the die, and are considered to have a value of 0.)

From page 13 of the RRG:

Setup:

6 - Players roll their starting character dice and add up the values rolled (the white numbers).

The example in the rules show the light side player rolling a blank, a ranged 1, and a melee +2 with a total value of 3. So modified values are counted.