Hello! It's exciting to hear about your upcoming trip to Denmark's cities of Roskilde, Ribe and Aalborg. I'm happy to provide you with some useful travel tips for these locations.

Best Time to Visit:
The best time to visit Denmark is during the months of May to August when the weather is pleasantly warm. But keep in mind, summer is also the most crowded season. If you want to avoid crowds, you can consider travelling in the shoulder season from September to October.

Route and Accessibility:
Copenhagen's major international airport, Kastrup, is the primary entry point for most visitors. From there, it's a short train ride to Roskilde. For reaching Aalborg and Ribe, you may take a train or bus. Denmark's transportation infrastructure is well-developed, making it easy to explore the cities.

Accommodation and Booking:
All three cities have varied accommodation options ranging from budget hostels to luxury hotels. Booking.com, Airbnb, and the local tourist websites can be used for reserving accommodation. It's advisable to book in advance during peak season.

Clothing and Essentials:
Denmark's weather can be unpredictable, so pack a mix of light and warm layers. Waterproof jackets and comfortable walking shoes are also recommended. Don't forget to pack essentials like travel adapter, toiletries, and necessary medications.

Health and Safety:
Denmark is traditionally a safe destination with low crime rates. The tap water is safe to drink. If you have specific dietary or medical requirements, check ahead with restaurants or medical facilities.

Local Etiquette and Respect:
Danish people value punctuality, so it's important to be on time for appointments or reservations. It's also common to say 'Tak' (Thank you) after receiving a service. When visiting churches or other religious monuments, dress respectfully and follow any posted signage.