Mostly in TSS teams its a good idea to keep a couple of pokemon who aren't resistant to sandstorm, because most of the rock/steel/ground pokemon have similar weaknesses. For instance, your team will have a difficult time dealing with milotcs, which are very common. I'd suggest putting a lanturn somewhere - maybe over cacturne seeing as you already have a better spiker in forry.
Tyranitar: I wouldnt put rest on something weak to ground attacks hen you don't have a heal beller - maybe use fire blast/dragon dance over it.
Cacturne: The set is fine, but I would replace it with something else.
Relicanth: This guy has too many weaknesses to rest, use toxic over it. It's SA is only 45 base, so if you wanted to use a water attack, use hydro pump, but I would put earthquake over it so you didn't have to sacrifice relicanths speed.
Magcargo: Uhm, magcargos attack stat is terrible, so, I would go with something like rock slide,over heat,toxic,protect, and concentrate on its defences. You might find cammerupt a possibility over this guy for an attacker with similar typing.
Forretress: giga drain is going to be doing nothing unless you plan to fight swamperts the whole time. Explosion rocks :]
Rhydon: Tyranitars sand stream works for the whole battle, so you probably wont need another sand stormer. I would use rock blast/rock tomb/hp rock over it.
I would take out a few of your rock types (notes 5x fighting weakness) and add some pokemon who arent resisting sand storm. Sure wou will take some more damage, but you aren't going to be wearing a team down with your toxicing and sandstorming if you get swept quickly :[
Hope I helped.