If you want to play the latest games with decent quality settings, you will need a separate ('discrete') graphics card ie GPU. Though some processors have a GPU on-board, and these are often quite capable, they will not be a replacement for a proper graphics card - this is reflected in there being no port for these on higher end gaming motherboards like the Asus ROG series (technically, the GPU is not 'exposed')
The graphics card is the most important component in speccing a gaming PC - go for an i5, 8Gb RAM, Crucial MX100 SSD, and the best graphics card you can afford