Roskilde is a fine place - have been there several times (i'm a dane so thats why
).
BUT...
1) check their overnighting prices - can be expensive! Landing fee for a PA28 is app. £10
2) No busses - cab from ap to the train station is app. £15-17
3) Train ticket to CPH app. £10 r/t.
There is only one alternative and that is EKGH. Its a private airfield with a 3000ft hard rwy and avgas only. PPR is the rule because of noise-procedures. See more on
www.ekgh.dk
EKGH is app. 45 min from CPH. You can walk in a slow pace to the train station in 15 min. or bike if you have a bike with you in 5 min.
Landing fee is high - £20 - but staying over for several nights is free. And camping is possible. There is a toilet but no showers or kitchen at the field. Only outside parking.
EKGH to Kronborg=Hamlet, Helsigoer, takes 20 min. by train. The Castle, Fredensborg Castle, is two minutes by train (one stop). Here lives the crown prince and his wife - and it is possible to walk the garden.
Downside w/EKGH: very quiet, no ils = if weather is bad (below 800ft) landing is difficult, can only be used 7-22 local time (but do have rwy-lights), and twice the ldg-price than ekrk.
Best, Maw