Survival: Roof (Hard) - Fire 'N Ice

Even if you survived almost all of the Survival levels, but, there's the hardest Survival level: Survival Roof (Hard). This is the Survival: Roof (Hard) Fire 'N Ice strategy.

Flag 1-2

 * Sunflower
 * Twin Sunflower
 * Repeater
 * Gatling Pea
 * Melon-pult
 * Winter Melon
 * Flower Pot
 * Potato Mine
 * Pumpkin

Flag 3-4

 * Twin Sunflower
 * Repeater
 * Gatling Pea
 * Melon-pult (optional, if less than 5 was planted)
 * Winter Melon
 * Torchwood
 * Pumpkin
 * Flower Pot
 * Imitater Pumpkin (optional)

Flag 5-8

 * Repeater
 * Gatling Pea
 * Winter Melon
 * Pumpkin
 * Imitater Pumpkin
 * Flower Pot
 * Umbrella Leaf
 * Squash
 * Jalapeno (optional)

​Flag 9-10

 * Repeater (optional, to backup killed Repeaters)
 * Gatling Pea (optional, to backup killed Gatling Peas)
 * Pumpkin
 * Imitater Pumpkin
 * Torchwood (optional, to backup killed Torchwoods)
 * Coffee Bean (optional)
 * Doom-shroom (optional)

Strategy
 Note:  The Garden Rake is strongly recommended.

First flags
Plant Sunflowers in the first and second columns as fast as possible. For the first zombie, let the Rake kills it. For the next ones, use Potato Mines. After having about 200 sun, plant Repeaters (and after that, Gatling Peas) from column 4 to 6 and plant Melon-pults (and after that, Winter Melons) in column 3.

Middle flags
Plant like the table below

The Catapult Zombies and Zombonis are your worst threats, even more than Gargantuars. Deal with Zombonis by Squashes/Jalapenos or pile tons of damage on them (the latter is quite hard). Catapult Zombies are less dangerous, but can still do quite some damage to your defense.

Final flags
Plant as many Pumpkins as possible. For the final wave, if you want, plant a Doom-shroom (with a Flower Pot and Coffee Bean, of course) in the middle of the zombies to eliminate most of them, but plant fast, as the Doom-shroom might get eaten by the zombies or smashed by the Gargantuars.

Trivia

 * This is one of the few strategies that uses Torchwood, Pea-shooting plants along with non-Kernel-pult movement-restricting plants.