DFRobot LCD shield minimum pin connections
It depends on what you want, just the lcd or the complete functionality of the shield   (lcd + buttons).

If you just want the lcd:
D4-D10
5V
GND  

If you want the lcd + buttons:
D4-D10
A0
5V
GND  

It is explained clearly in the manual: ( @ pin allocation)
http://www.dfrobot.com/wiki/index.php?title=Arduino_LCD_KeyPad_Shield_(SKU:_DFR0009)  

The rest of the pins are there for other shields to stack below / above it.  

Edit:
Here are the schematics:
http://www.dfrobot.com/image/data/DFR0009/LCDKeypad%20Shield%20V1.0%20SCH.pdf

It uses 5V because the VCC pin on the schematic matches the +5V pin on the arduino Uno 

In the schematic you can also see that the other pins are not used.