The live rock has nothing to do with rising your PH. Your substrate has evrything to do with it. Since you just started it you can add a PH chemical called Marine Buffer its made by seachem it works very good. I use it for when I add water. But your substrate will keep your PH up. Another thing so you dont worry is that you will get PH fluctuations through out the day. Meaning your PH will be highier in the morning/evening and lower during the day, This is natural. As for your ammonia/nitrate. If you have fish cut back on the feeding till the ammonia. For the nitrate if it isn't above 20ppm you are still fine. You will never be able to get nitrate to zero because food you feed your fish contains protein and protein leads to nitrate. I have tested my water before andd the PH would be 7.4-7.8 and then later on would read over 8.0. For the substrate I used 1.5 bags of Aroganite Sand mixed with 1 bag of live sand. If you have anymore questions feel free to PM me.