The {esc}(s#T sequence is part of a full primary font selection sequence.
Such a sequence can only select what is there; it does not create a font if it is not resident on the printer; if an exact match cannot be found, the printer substitutes the closest match, according to a predefined set of selection precedence rules.
As far as I am aware, none of the standard LaserJet models includes either the Kosmo or ArialBlack typefaces within the built-in resident set, so you could only use these if you do one of the following:
(1) Purchase a font cartridge (DIMM) holding the required fonts, and plug this into a spare slot on the device. Disadvantage is that cartridge can only be used on one device at a time.
(2) Purchase downloadable PCL format soft font equivalents of the PC-based fonts; these could be in bitmap format (i.e. single size) or scalable (either Intellifont (PCLEO) or TrueType (PCLETTO) encapsulated formats). Advantage is they could be downloaded to multiple devices.
(3) If you have the Windows TrueType versions of these fonts, some applications (e.g. Word) in conjunction with the printer driver, will generate an on-the-fly encapsulated PCL font (or rather, just a subset of this containing the characters to be printed from the document) and download this within the output print stream.