How much total Hard Disk Space is required to create swap partition
For the swap partition, you need an amount of hard disk space equal to the size of swap partition that you intend to create. The swap partition that you need is a function of the workload of the server, and while it sounds as if a server with this much memory might not need a swap parttiton (depending on workload, about which you have given no information), I would always try to include at least a small swap partition, so that in the case of problems the server fails gracefully rather than sudenly coming to a halt.
How much total Hard Disk Space is required ... for root partition.
The root partition needs to have enough space for everything that is going to go onto the root partition.
Some people prefer to use several (many) partitions for their system, and others prefer the 'one large partition' approach. This makes a large difference to how much goes into the root partition and how much goes onto these other partitions. If disk space is limited, generally, fewer partitions is easier to configure.
Some systems need more applications programs installed than others. This makes a big difference (but, depending on your partitioning system, this may not be part of your root filesystem).
If this box is going to be a fileserver, then it would be necessary to have the space for the files that it is going to serve (but again the files served may or may not be part of the root filesystem).