Yes, you should be able to use the same SYBR green mastermix for both reactions; however, please note that the methods for RNA isolation, cDNA conversion, and primer design to interrogate microRNAs are not the same as for typical mRNAs. For microRNAs, I would suggest using either Exiqon's kits
http://www.exiqon.com/microrna-real-time-pcr or the Taqman microRNA assays from Applied Biosystems (although Taqman isn't based on SYBR green).