SKSpriteNode – create a round corner node?

To get a rounded corner node you can use 2 approaches, each of them requires use of SKShapeNode.

First way is to use SKShapeNode and set its path to be a rounded rectangle like this:

SKShapeNode* tile = [SKShapeNode node];
[tile setPath:CGPathCreateWithRoundedRect(CGRectMake(-15, -15, 30, 30), 4, 4, nil)];
tile.strokeColor = tile.fillColor = [UIColor colorWithRed:0.0/255.0
                                                    green:128.0/255.0
                                                     blue:255.0/255.0
                                                    alpha:1.0];

The other one uses sprite node,crop node and SKShapeNode with rounded rectangle as crop nodes mask:

SKSpriteNode *tile = [SKSpriteNode spriteNodeWithColor:[UIColor   colorWithRed:0.0/255.0
                                                                           green:128.0/255.0
                                                                            blue:255.0/255.0
                                                                           alpha:1.0] size:CGSizeMake(30, 30)];
SKCropNode* cropNode = [SKCropNode node];
SKShapeNode* mask = [SKShapeNode node];
[mask setPath:CGPathCreateWithRoundedRect(CGRectMake(-15, -15, 30, 30), 4, 4, nil)];
[mask setFillColor:[SKColor whiteColor]];
[cropNode setMaskNode:mask];
[cropNode addChild:tile];

If your tiles are one solid colour, i suggest you go with the first approach.