I'm clearly missing something.

Troy

\setupinteraction[state=start]
\defineconversionset[frontpart:pagenumber][][romannumerals]
\defineconversionset[bodypart:pagenumber][][numbers]
\defineconversionset[appendix:pagenumber][][Characters]
\setupuserpagenumber[numberconverionset=pagenumber,way=byblock]
\placebookmarks[chapter,section][chapter][force=yes]
\starttext
    \startfrontmatter
        \startchapter[title={Cover}]\stopchapter
        \dorecurse{2}{\mbox{}\page}

        \setupuserpagenumber[viewerprefix=titlepage]
        \startstandardmakeup
            \startchapter[title={Title Page}]
            \stopchapter
        \stopstandardmakeup
        \setupuserpagenumber[viewerprefix=p ]

    \stopfrontmatter

   \startbodymatter

   \stopbodymatter

\stoptext