The Roboto spec book shows "Black Small Caps" but it's not included in the font package. Fallback is using Black in uppercase - not ideal.
Opentype/Truetype fonts can embed a small-caps variant of the font inside the same font, and this can be activated using Opentype typographic features (which can be embedded into any Truetype, Opentype or derived font including WOFF and EOT).
So you would use the "Black" font, but activate the "smcp" Opentype feature in whatever software you're using. It'll probably be called "Small Caps" if you're using graphic design or word processing software. Or if you are implementing this in software, you'll need to figure out how to activate Opentype typographic features in whatever API you're using, and activate the "smcp" one.
If the font you're using doesn't support this feature, you either won't get small caps or your software will try to create "fake small caps" from the existing capital letters.
The small caps variant of a font will not just be the capital letters shrunk down, because that would also reduce the thickness of the strokes. Instead, the small caps variant will designed to have the same stroke thickness, and probably also the same or scaled counters (usually resulting in shorter and fatter letters) as the capitals, meaning they'll look bolder than if you had just shrunk the capital letters.
There is no available downloadable font called Black Small Caps. This is because the font itself is created with whatever word processor you are using. For example, in Photoshop i can create "Black Small Caps" of "Roboto" by selecting "Roboto" as the font, "Black" as the Font Style, and then going to the Character/Paragraph panel and applying "Small Caps".
If you are trying to implement the font style within your design, it should be possible in most design programs. If you are trying to do this in code, I can only assume that Android allows you to apply "Small Caps" to the font "Roboto Black" when called for in styling code.
Here is what the font looks like as "Roboto Black (Small Caps)" and as "Roboto Black" as applied in Photoshop: