Gol D. Roger was known as the Pirate King, the strongest and most infamous being to have sailed the Grand Line. The capture and death of Roger by the World Government brought a change throughout the world. His last words before his death revealed the location of the greatest treasure in the world, One Piece. It was this revelation that brought about the Grand Age of Pirates, men who dreamed of finding One Piece (which promises an unlimited amount of riches and fame), and quite possibly the most coveted of titles for the person who found it, the title of the Pirate King.

Enter Monkey D. Luffy, a 17-year-old boy that defies your standard definition of a pirate. Rather than the popular persona of a wicked, hardened, toothless pirate who ransacks villages for fun, Luffy’s reason for being a pirate is one of pure wonder; the thought of an exciting adventure and meeting new and intriguing people, along with finding One Piece, are his reasons of becoming a pirate. Following in the footsteps of his childhood hero, Luffy and his crew travel across the Grand Line, experiencing crazy adventures, unveiling dark mysteries and battling strong enemies, all in order to reach One Piece.

(Source: MAL Rewrite)

Romance Dawn refers to three separate manga chapters drawn by artist Eiichiro Oda between 1996 and 1997, culminating in the first chapter of the ongoing series One Piece. The first volume of this series is also called "Romance Dawn;" for this, please see One Piece manga releases: vol. 1.
"Romance Dawn" represents the slow progression of the author's ideas in his desire to create a manga about pirates, whose inspiration was drawn largely from his own childhood interests. While a first-year junior high school student, he began sketching out ideas for a pirate-themed manga in a notbeook, in pencil. Years later, as an assistant to Rurouni Kenshin author Nobuhiro Watsuki, he began refining his ideas into what would become "Romance Dawn," and later, One Piece. All 3 versions were published in Weekly Shonen Jump magazine, with the final incarnation published exactly one year after the first. The author made significant alterations to the premise and plot over the course of the three chapters, which will be examined in-depth below.
(Source: One Piece Wiki)

A collection of short stories drawn by Oda Eiichiro before One Piece became a major hit. Includes chapter called 'Romance Dawn' which was later re-envisioned as 'One Piece'.

A Collection of One-shots by Oda Eiichiro done prior to the debut of One Piece.

Titles included are:
1) Wanted!
2) God's Gift For The Future
3) Ikki Yako
4) Monsters
5) Romance Dawn

One Piece Databook