Can I use Houndoom's "Single Strike Roar" Ability if all four Single Strike Energy cards are in play or in the discard pile?
No you cannot. Since the location of all four Single Strike Energy cards are known, there's no way Single Strike Roar would be able to find one during a deck search.
Source: TPCi Rules Team (2021-03-25)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH5_96
SWSH5_96
SWSH5_141
SWSH5_141