Rolick Desert starts off right away with an interesting screen—you'll notice a river running east-west through it. There isn't much you can do here now, but if you return later with the Aqua Boots you'll find a cheap Life Potion and Purple Mea.
For now, though, head north. You'll immediately find a Life Potion which you should be able to afford with just a few Blue Snake kills. From here, you need to formulate your plan of attack. Rolick Desert is not very wide, but it runs quite far vertically. A ridge in the center makes the whole area a big circle, with a small area off to the southwest where you will find Rolick. It's generally more efficient to head east and go counter-clockwise, but you may want to pick up the cheap Bible (800 gold) just west of the entrance first.
If you head east, you will soon encounter Green Frogs for the first time. Like snakes, they jump, but they do so at two different heights, so their movement is somewhat unpredictable if you're not paying close attention. They always cross the screen in a direct horizontal line, though. It's usually best to catch them with a sustained sword stroke on the landing. You'll run into another new enemy, Red Porcupigs, on the next screen. They are a pretty standard foe, and don't drop much gold. The only thing to watch out for is their charge attack, which they will use if they are ever on the same horizontal plane with you.
You'll find a number of interesting things in the caves on the east side of Rolick Desert. Aruzasu's Shield is a tease—at 8,000 gold, you can't possibly afford it until you defeat Rolick and find more Bibles than are available at this point. Winkle will give you a password, which will let you continue the game if you turn the system off. Pink Moles guard a Bible being sold for a hefty 2,000 gold. If you need money, head north and fight Green Snakes. They take two sustained sword blows to kill, but yield a whopping 180 gold per kill—and you'll find Randar nearby in case your health gets low!
You'll find a Life Potion being sold for 800 gold at the north end of the ridge, at which point you should start heading south and west. Once you defeat Rolick, you'll need to return north of here to get the second Crystal, but first things first.
When you run into Gray Water Spirits on the west side of the ridge, take a moment to hunt down and kill four of them. This will open a cave where you can purchase Green Mea for 1,000 gold. Green Mea is not sold nearly as cheaply anywhere else in the game, so take advantage of this opportunity.
You'll find a new friend, Enny, in an open cave on the west side of the area. Like Randar, Enny will heal you, but she charges 50 gold per individual life meter. Randar is generally a more efficient healer, and if you need little enough life that Enny's services are cheaper (i.e., less than 3 bars), you can probably go without healing. Still, it pays to remember where Enny is in case you can't reach Randar.
Rolick Cave
When you're done exploring, head to the southwest corner of the desert. (Make sure your gold maximum is at 6,000.) Rio tells you to "push the blue rock" to open Rolick Cave, but as you can see, this is not the most helpful hint. You actually don't need to "push" a blue rock at all—you actually need to hit one with your sword five times. Specifically, hit the southeastern rock on the inner circle. Be careful to avoid the Aqua Bats and Green Frogs as you do so.
This is a side-scrolling dungeon like the Valley Entrance, but unlike that dungeon, here you can be forced out if you touch the left side of the screen. Since the dungeon doesn't auto-scroll, that is only likely to happen if you are pushed by an enemy, or reach a dead end and have no choice. The first big obstacle to this effect is a zig-zagging floor covered in Red Snakes. The floor design makes it unlikely that you will be pushed out of the dungeon, but you'll still want to try to jump over them entirely. Watch out for Fire Spirits immediately after that. These enemies come at you in a sinuous motion, and are usually best avoided.
You'll encounter a pair of Giant Snakes, but they have no new tricks. Be careful when you see a line of Red Snakes that you can't reach, though. There is a tricky jump ahead, and if you miss and land on a Red Snake, you can start a chain reaction that will knock you right out of the dungeon. Likewise, don't fall from the floating blocks after that, or you'll have to start over.
There is a puzzle element ahead, though it's not exactly rocket science. You'll hit an apparent dead end. Simply attack the blocks and decorative helmet at the end, and the platform you're standing on will lower. You'll see this mechanic a lot in future side-scrolling dungeons. Once you pass this last obstacle, you'll find yourself facing Rolick.
Rolick doesn't fire any projectiles, but he is still a dangerous foe. His touch deals almost an entire life bar of damage, and he can be hard to avoid. He will alternate between simply sitting there exposed, and rolling into a spiky ball and coming after you. You can hit him even when rolled up, but doing so is very dangerous. A conservative approach, only attacking when he's standing still, is safer and just as effective. You'll get a lot of practice dodging Rolick's rolls in this fight, but once you're victorious you'll be that much closer to your goal—and that much richer.
As with Despa, defeating Rolick will reveal the path to the next area (in the form of a bridge at the northwest corner of the area, as well as the wise woman selling the second Crystal, which will cost you 3,000 gold. Pick it up if you're willing to spend the money, then head north to the Graveyard of Bachular.